MAIN  IJBK *>RY- 


ft'i'. 

LIBRARY 
G 


AN  INTRODUCTION  TO  THE  STUDY 


COMPOUNDS    OF    CARBON 


OR 


ORGANIC   CHEMISTRY    , 


BY 
IRA   REMSEN 


FIFTH  REVISION 


D.  C.  HEATH  &  CO.,  PUBLISHERS 
BOSTON    NEW  YORK    CHICAGO 


\*&* 


COPYRIGHT,  1885,  i501,  1903,  AND  1909, 
BY  IKA  REMSEN 

I  K9 
MAIN  LIBRARY.AGRICULTURE  DEFT, 


PREFACE  TO  FIRST  EDITION 


THIS  book  is  intended  for  those  who  are  beginning  the  subject. 
For  this  reason,  special  care  has  been  taken  to  select  for  treatment 
such  compounds  as  best  serve  to  make  clear  the  fundamental  prin- 
ciples. General  relations  as  illustrated  by  special  cases  are  discussed 
rather  more  fully  than  is  customary  in  books  of  the  same  size  ;  and, 
on  the  other  hand,  the  number  of  compounds  taken  up  is  smaller 
than  usual.  The  author  has  endeavored  to  avoid  dogmatism,  and 
to  lead  the  student,  through  a  careful  study  of  the  facts,  to  see  for 
himself  the  reasons  for  adopting  the  prevalent  views  in  regard  to  the 
structure  of  the  compounds  of  carbon.  Whenever  a  new  formula  is 
presented,  the  reasons  for  using  it  are  given  so  that  it  may  afterward 
be  used  intelligently.  It  is  believed  that  the  book  is  adapted  to  the 
needs  of  all  students  of  chemistry,  whether  they  intend  to  follow 
the  pure  science,  or  to  deal  with  it  in  its  applications  to  the  arts, 
medicine,  etc.  It  is  difficult  to  see  how,  without  some  such  general 
introductory  study,  the  technical  chemist  and  the  student  of  medicine 
can  comprehend  what  is  usually  put  before  them  under  the  heads 
of  "Applied  Organic  Chemistry"  and  "Medical  Chemistry." 

Without  some  direct  contact  with  the  compounds  considered,  it 
is  impossible  to  get  a  clear  idea  regarding  them  and  their  changes. 
A  course  of  properly  selected  experiments,  illustrating  the  methods 
used  in  preparing  the  principal  classes  of  compounds,  and  the  funda- 
mental reactions  involved  in  their  transformations,  wonderfully  facili- 
tates the  study.  The  attempt  has  been  made  to  give  directions  for 
such  a  course.  More  than  eighty  experiments  which  could  be  per- 
formed in  any  chemical  laboratory  are  described;  and  it  is  hoped 
that  the  plan  may  meet  with  approval.  The  time  required  to 
perform  a  fair  proportion  of  these  experiments  is  not  great;  and 
the  results  in  the  direction  of  enlarging  the  student's  knowledge 
of  chemical  phenomena,  will,  it  is  firmly  believed,  furnish  a  full 
compensation  for  the  time  spent. 

iii 

48060 


iv  PREFACE. 

The  order  in  which  the  topics  are  taken  up  will  be  found  to  differ 
somewhat  from  that  commonly  adopted.  The  object  in  view  was, 
however,  not  to  find  a  new  method,  but  to  find  one  which  would 
bring  out  as  clearly  as  possible  the  beauty  and  simplicity  of  the 
relations  which  exist  between  the  different  classes  of  carbon  com- 
pounds. The  reasons  for  the  method  used  are  given  in  the  body 
of  the  book. 


PREFACE  TO   FOURTH   REVISION. 

THE  important  advances  that  have  been  made  in  the  field  of 
organic  chemistry  during  the  past  few  years  have  made  a  thorough 
revision  of  this  book  necessary.  The  present  edition  gives  the  results 
of  the  revision.  The  principal  changes  and  additions  will  be  found 
in  the  chapters  dealing  with  the  Sugars,  Stereoisomerism,  the  Diazo 
Compounds,  and  the  Terpenes.  The  treatment  of  the  Aromatic 
Compounds  is,  in  general,  fuller  than  in  the  older  editions.  Although 
considerable  has  been  added,  the  size  of  the  volume  has  not  been 
markedly  increased,  the  difference  between  the  last  edition  and  the 
present  being  only  about  fifty  pages.  In  addition  to  the  changes 
indicated  above,  minor  changes  have  been  made  throughout,  and 
the  author  believes  that  the  book  is  now  fully  in  harmony  with  the 
present  state  of  organic  chemistry. 


PREFACE   TO   FIFTH   REVISION 

ADVANTAGE  has  been  taken  of  the  resetting  of  this  book  to  make 
a  number  of  changes  that  were  called  for,  and  the  author  believes 
that  it  has  been  much  improved.  He  gladly  acknowledges  his  indebt- 
edness to  Professor  W.  R.  Orndorff  of  Cornell  University  for  many 
valuable  suggestions.  Professor  Orndorff  has  used  the  book  for  a 
number  of  years  with  large  classes,  and  the  author  has  reaped  the 
benefit  of  his  experience. 


CONTENTS 

CHAPTER  I 
Introduction 

PAOB 

Sources  of  compounds.  —  Purification  of  the  compounds.  —  Deter- 
mination of  the  boiling-point.  —  Determination  of  the  melting- 
point.  —  Analysis.  — Formula.  —  Structural  formula.  — General 
principle  of  classification  of  the  compounds  of  carbon  .  .  1 

CHAPTER  II 

Methane  and  Ethane.  —  Homologous  Series 
Methane. — Ethane ,        .21 

CHAPTER  III 

Halogen  Derivatives  of  Methane  and  Ethane 

Substitution.  —  Chlor-methane,  Brom-methane,  lodo-methane. — Di- 
iodo-methane.  —  Chloroform,  bronioform,  iodoform.  —  Chlor- 
ethane,  Brom-ethane,  lodo-ethane.  —  Isomerism  ...  27 

CHAPTER  IV 
Oxygen  Derivatives  of  Methane  and  Ethane 

Alcohols.  —  Methyl  alcohol.  —  Ethyl  alcohol.  —  Fermentation.  — 
Denatured  alcohol.  —  Alcoholic  beverages.  —  Ethers.  —  Ethyl 
ether.  —  Mixed  ethers.  —  Aldehydes.  —  Formic  aldehyde.  — 
Acetic  aldehyde.  —  Paraldehyde.  —  Metaldehyde.  —  Chloral. 
—  Acids.  —  Formic  acid.  —  Acetic  acid.  —  Acetic  anhydride.  — 
Acetyl  chloride,  bromide,  iodide.  —  Ethereal  salts  or  esters.  — 
Ketones  or  acetones 35 

CHAPTER  V 

Sulphur  Derivatives  of  Methane  and  Ethane 
Mercaptans.  —  Ethyl   mercaptan.  —  Sulphur   ethers.  —  Sulphonic 

acids 75 


Vi  CONTENTS 

CHAPTER   VI 

Nitrogen  Derivatives  of  Methane  and  Ethane 

PAGE 

Cyanogen.  —  Hydrocyanic    acid.  — Cyanides.  —  Cyanuric    acid.  — 
Sulpho-cyanic  acid.  —  Cyanides.  —  Isocyanides  or  carbamines. 

—  Cyanates  and  isocyanates. — Sulpho-cyanates. — Isosulpho- 
cyanates  or  mustard  oils.  —  Substituted  ammonias  or  amines. 

—  Hydrazine  compounds. — Nitro-conipounds. — Nitroso-   and 
isonitroso-compounds.  —  Fulminic  acid      .....      80 

CHAPTER  VII 

Derivatives  of  Methane  and  Ethane  containing 
Phosphorus,  Arsenic,  etc. 

Phosphorus    compounds. — Arsenic    compounds. — Zinc    ethyl. — 

Sodium  ethyl.  —  Retrospect        .        .        .  .        .        .104 


CHAPTER  VIII 
The  Hydrocarbons  of  the  Marsh-Gas  Series,  or  Paraffins 

Petroleum.  —  Synthesis  of  paraffins.  —  Isomerism  among  the  paraf- 
fins. —  Hexanes  ...  .  • 109 

CHAPTER   IX 

Oxygen  Derivatives  of  the  Higher  Members  of  the 
Paraffin  Series 

Alcohols.  —  Normal  propyl  alcohol. — Secondary  propyl  alcohol. — 
Secondary  alcohols  —  Butyl  alcohols.  —  Pentyl  or  amyl  alco- 
hols. —  Aldehydes.  —  Acids.  —  Fatty  acids.  —  Propionic  acid. 
—  Butyric  acids.  —  Valeric  acids.  —  Palmitic  acid.  —  Stearic 
acid.  —  Soaps. — Polyacid  alcohols  and  polybasic  acids.  —  Di- 
acid  alcohols.  —  Ethylene  alcohol  or  glycol.  —  Dibasic  acids.  — 
Oxalic  acid.  —  Malonic  acid. — Succinic  acids. — Pyrotartaric 
acid. — Tri-acid  alcohols.  —  Glycerol. — Ethereal  salts  of  glyc- 
erol.  —  Fats.  —  Tribasic  acids.  —  Tetr-acid  alcohols.  —  Pent- 
acid  alcohols.  —  Hex-acid  alcohols.  —  Hept-acid  alcohols,  etc.  .  121 


CONTENTS  yii 

CHAPTER   X 
Mixed  Compounds.  —  Derivatives  of  the  Paraffins 

PAGE 

Hydroxy-acids,  CnH2n03.  —  Carbonic  acid.  —  Glycolic  acid.  — Lactic 
acids.  —  Hydracry  liu  acid.  —  Physical  isomerism  —  Hydroxy- 
sulphonic  acids.  — Isethionic  acid.  — Lactones.  —  Hydroxy-acids, 
CnH2n04. — Glyceric  acid.  —  Other  Hydroxy-monobasic  acids. 

—  Harmonic  acids.  —  Gluconic   acids,   etc.  —  Hydroxy-acids, 
CnH2n-20s.  —  Tartronic  acid.  —  Malic   acids.  —  Hydroxy-acids, 
CnH2n-2O6.  —  Mesoxalic  acid.  —  Tartaric  acid.  — Racemic  acid. 

—  Inactive  tartaric  acid.  —  Hydroxy-acids,  CnH2n-4O7. — Citric 
acid.  —  Hydroxy-acids,   CnH2n-208.  —  Saccharic   acid.  — Mucic 
acid  ,    157 


CHAPTER  XI 
Carbohydrates 

Monosaccharides.  — Trioses  and  tetroses.  —  Glycerose. — Erythrose. 

—  Pentoses.  — Arabinoses.  —  Xylose.  — Ribose.  — Rhamnose. — 
Hexoses.  —  Glucose.  —  Fructose.  —  Man  nose.  —  Galactose.  — 
Gulose.  —  Polysaccharides  or  complex  sugars.  —  Cane  sugar.  — 
Sugar  of  milk.  —  Maltose.  —  Polysaccharides  that  are  not  sugars. 

—  Cellulose.  —  Gun  cotton.  —  Paper.  —  Starch.  —  Glycogen.  — 
Dextrin.  —  Gums  185 


CHAPTER   XII 
Mixed  Compounds  containing  Nitrogen 

Ammo-acids.  —  Amino-formic  acid.  —  Glycocoll.  —  Sarcosine. — Am- 
ino-propionic  acids.  —  Leucine.  —  Serine.  —  Cystine.  —  Amino- 
sulphonic  acids.  —  Taurine.  —  Amino-dibasic  acids.  —  Aspartic 
acid. — Acid  amides.  —  Hofmann's  reaction. — Amic  acids. — 
Asparagine.  —  Succinimide.  —  Cyanimides.  —  Calcium  cyan- 
amide.  —  Guanidine.  —  Creatine.  —  Creatinine.  —  Urea  or  carb- 
amide and  derivatives.  —  Substituted  ureas.  —  Ureids.  —  Para- 
banic  acid.  —  Oxaluric  acid.  —  Barbituric  acid.  —  Sulpho  urea. 
—  Uric  acid.  —  Xan thine.  —  Theobromine.  —  Caffeine.  —  Gua- 
nine.  —  Polypeptides.  —  Retrospect  .  • 205 


Vlll  CONTENTS 

CHAPTER   XIII 

Unsaturated  Carbon  Compounds.  —  Distinction  between 
Saturated  and  Unsaturated  Compounds 

PAGE 

Ethylene    and    its    derivatives.  —  Ethylene.  —  Alcohols,    CDH2nO. 

—  Allyl  alcohol.  —  Allyl    mustard    oil.  —  Acrolein.  —  Acids, 
CnH2Q_202.  —  Acrylic  acid.  —  Crotonic  acids.  —  Oleic  acid.  — 
Polybasic  acids  of  the  ethylene  group.  —  Fumaric  and  maleic 
acids. — Acids,  C5H604. — Aconitic  acid. — Acetylene  and  its 
derivatives.  —  Acetylene.  —  Propargyl      alcohol.  —  Acids, 
CnH2n-402.  —  Propiolic  acid.  —  Tetrolic  acid.  —  Sorbic  acid.  — 
Linolei'c  acid.  —  Valylene.  —  Dipropargyl  ....     228 

CHAPTER   XIV 

The  Benzene  Series  of  Hydrocarbons.  —  Aromatic 
Compounds 

Benzene.  —  Toluene.  —  Xylenes.  —  Ethyl-benzene.  —  Mesitylene.  — 
Pseudocumene.  —  Cymene.  —  Hexahydrobenzenes,  naphthenes. 
— Hexamethylene.  —  Tetrahydrobenzenes.  —  Tetrahydrotolu- 
ene.  —  Hydrocarbons,  Ci0Hi8.  —  Hydrocamphene.  —  Menthene. 

—  Dihydrobenzenes    . 254 

CHAPTER   XV 

Derivatives  of  the  Hydrocarbons,  CnH2n-6,  of  the 
Benzene  Series 

Halogen  derivatives  of  benzene.  —  Chlor-benzene.  — Brora-benzene. 

—  lodo-benzene.  —  Phenyliodoso    chloride.  —  lodoxy-benzene. 

—  Diphenyliodonium    hydroxide.  —  Dibrom-benzene.  —  Halo- 
gen derivatives  of  toluene.  —  Halogen  derivatives  of  the  higher 
members  of  the  benzene  series.  —  Nitro  compounds  of  benzene 
and  toluene. — Mono-nitro-benzene.  —  Dinitro-benzene. — Nitro- 
toluenes. — Ammo  compounds  of  benzene,   etc. — Aniline. — 
Dimethyl-aniline.  —  Diphenylamine.  —  Acetanilide.  —  Tolui- 
dines.  —  Diazo  compounds    of    benzene.  —  Diazo-amino    com- 
pounds. —  Azo-benzene.  —  Hydrazo-benzene.  —  Hydrazines.  — 
Phenylhydrazine.  —  Methylphenylhydrazine.  —  Sulphonic  acids 
of  benzene.  — Sulphanilic  acid.  —  Helianthin.  — Diphenylamine 
orange.  —  Phenols,  or  hydroxyl  derivatives  of  benzene,  etc.  — 


CONTENTS  ix 


Mon-acid  phenols.  —  Phenol.  —  Methyl-phenyl  ether.  —  Tri- 
nitro-phenol.  —  Amino-phenols.  —  Phenol-sulphonic  acids.  — 
Phenyl  mercaptan.  — Cresols.  — Thymol. — Di-acid  phenols.  — 
Pyrocatechol.  —  Guaiacol.  —  Resorcinol.  —  Styphnic  acid. — 
Hydroquinol.  —  Orcinol.  —  Tri-acid  phenols.  —  Pyrogallol.  — 
Phloroglucinol. — Alcohols  of  the  benzene  series.  —  Benzyl  alco- 
hol. —  Aldehydes  of  the  benzene  series.  —  Oil  of  bitter  almonds. 

—  Cuminic  aldehyde.  —  Benzaldoximes.  —  Acids  of  the  benzene 
series.  —  Monobasic  acids,  CnH2n_802.  —  Benzoic  acid.  —  Ben- 
zoyl  chloride.  —  Substitution-products  of  benzoic  acid.  —  Nitro- 
benzoic  acids.  —  Anthranilic  acid.  —  Isatine.  —  Hippuric   acid. 

—  Sulpho-benzoic    acids.  —  Toluic    acids.  —  a-Toluic    acid.  — 
Oxindol.  —  Mesitylenic  acid.  —  Hydro-cinnamic  acid.  —  Hydro- 
carbostyril.  —  Dibasic    acids,   CnH2n-ioO4.  —  Phthalic    acid.  — 
Isophthalic  acid.  — Terephthalic  acid.  —  Hexabasic  acid.  — Mel- 
litic  acid. — Phenol-acids,  or  Hydroxy-acids  of  the  benzene  series. 

—  Salicylic   acid.  —  Salol.  —  Oxybenzoic  acid.  —  Para-oxyben- 
zoic  acid.  —  Anisic  acid.  —  Di-hydroxy-benzoic  acids,  C7H604.  —    • 
Protocatechuic  acid.  —  Vanillic  acid.  —  Vanillin.  —  Piperonal.  — 
Tri-hydroxy-benzoic  acids,  C7H6O5. — Gallic  acid.  — Tannic  acid. 
Ketones  and  allied  derivatives  of  the  benzene  series.  —  Quinones. 

—  Pyridine  bases.  —  Pyridine.  —  Lutidines.  —  Conyrine.  —  Co- 
nine.— Terpenes  and  camphors. —  Hemiterpenes. — Terpenes. — 
Monocyclic  terpenes. — Bicyclic  terpenes. — Pinene. —  Oil  of  tur- 
pentine.—Camphene. —  Camphane. — Sesqui-  and  polyterpenes. 

—  Caoutchouc. — Camphors. — Monocyclic  camphors.—  Bicyclic 
camphors.— Borneol.— Camphor.— Artificial  camphor.— Geraniol    277 

CHAPTER   XVI 

Di-phenyl-methane,  Tri-phenyl-methane,  Tetra-phenyl- 
methane,  and  their  Derivatives 

Tri-phenyl-methane.    —  Trinitro-triphenyl-methane.   —  Triamino- 
triphenyl-methane. — Tri-phenyl-methane  dyes.  — Aniline  dyes. 

—  Para-rosaniline.  —  Rosaniline.  —  Hexa-methyl  para-rosani- 
line.  —  Phthaleins.  —  Phenol-phthalem.  —  Fluoresce'in.  —  Eosin    362 

CHAPTER  XVII 

Hydrocarbons,  CnH2n-8,  and  Derivatives 
Styrene.  —  Styryl  alcohol.  —  Cinnamic  acid.— Nitro-cinnamic  acids. 

—  Amino-cinnamic  acids.  —  Coumarin        ...  •     374 


X  CONTENTS 

CHAPTER   XVIII 
Phenyl-acetylene  and  Derivatives 

PAGE 

Phenyl-acetylene.  —  Phenyl-propiolic  acid.  —  Ortho-nitro-phenyl- 
propiolic  acid.  —  Indigo  and  allied  compounds.  —  Indigo-blue. 
—  Indigo-white.  —  Indol.  —  Skatol 380 

CHAPTER   XIX 

Hydrocarbons  containing  Two  Benzene  Residues  in 
Direct  Combination 

Diphenyl. —  Benzidine.  —  Carbazol.  —  Naphthalene.  —  Derivatives 
of  naphthalene.  —  Naphthylaraines.  —  Naphthols.  —  Quinoline 
and  analogous  compounds.  —  Quinoline.  —  Quinaldine.  —  Lepi- 
dine.  —  Carbostyril.  —  Isoquinoline  ......  386 

CHAPTER   XX 

Hydrocarbons  containing  Two  Benzene  Residues  in 
Indirect  Combination 

Anthracene.  —  Anthraquinone.  —  Alizarin.  —  Purpurin.  —  Phenan- 

threne  ,     407 


CHAPTER   XXI 
Glucosides.  —  Alkaloids,  etc. 

JEsculin.  —  Amygdalin.  —  Arbutin.  —  Coniferin.  —  Helicin.  —  My- 
ronic  acid.  —  Phloridzin.  —  Salicin.  —  Saponin.  —  Alkaloids.  — 
Quinine.  —  Cinchonine.  —  Cocaine.  —  Nicotine.  —  Stropine.  — 
Tropine.  —  Morphine.  —  Codeine.  —  Narcotine.  —  Piperine.  — 
Piperidine.  —  Strychnine.  —  Albumin.  —  Peptones  .  .  .415 

INDEX  ,     421 


CHEMISTRY 

OF  THE 


COMPOUNDS   OF  CARBON 


CHAPTER  I 
INTRODUCTION 

IN  studying  the  compounds  of  carbon,  one  cannot  fail  to 
be  struck  by  their  large  number,  arid  by  the  ease  with  which 
they  undergo  change  when  subjected  to  various  influences. 
Mainly  on  account  of  the  large  number,  though  partly  on 
account  of  peculiarities  in  their  chemical  conduct,  it  is  custom- 
ary to  treat  of  these  compounds  by  themselves.  At  first, 
General  Chemistry  was  divided  into  Inorganic  and  Organic 
Chemistry,  as  it  was  believed  that  there  were  fundamental 
differences  between  the  compounds  included  under  the  two 
heads.  Those  compounds  which  form  the  mineral  portion  of 
the  earth  were  treated  under  the  first  head,  while  those  which 
were  found  ready  formed  in  the  organs  of  plants  or  animals 
were  the  subject  of  organic  chemistry.  It  was  believed  that, 
as  the  organic  compounds  are  elaborated  under  the  influence 
of  the  life  process,  there  must  be  something  about  them  which 
distinguishes  them  from  the  inorganic  compounds  in  whose 
formation  the  life  process  has  no  part.  Gradually,  however, 
this  idea  has  been  abandoned ;  for,  one  by  one,  'many  of  the 
compounds  which  are  found  in  plants  and  animals  have  been 
made  in  the  chemical  laboratory,  and  without  the  aid  of  the 
life  process.  The  first  instance  of  the  artificial  preparation  of 
an  organic  compound  was  that  pf  urea.  This  substance  was 
obtained  by  Wohler_in  1828  from  ammonium  cyanate.  When 
a  water  solution  of  the  latter  is  evaporated  on  a  water  bath, 

1 


INTRODUCTION 


urea  is  deposited.  Up  to  the  time  of  Wohler's  discovery,  the 
formation  of  urea,  like  that  of  other  organic  compounds,  was 
thought  to  be  necessarily  connected  with  the  life  process; 
but  it  was  thus  shown  that  it  could  be  formed  without  the 
intervention  of  life.  Afterward,  it  was  shown  that  potassium 
cyanide  can  be  made  by  passing  nitrogen  over  a  heated  mixture 
of  carbon  and  potassium  carbonate;  and,  as  potassium  cyanate 
can  be  made  from  the  cyanide  by  oxidation,  it  follows  that 
urea  can  be  made  from  the  elements.  Finally,  in  1856,  Berthe- 
lot  succeeded  in  making  potassium  formate  by  passing  carbon 
monoxide  over  heated  potassium  hydroxide  ;  and  in  making 
acetylene,  a  compound,  the  composition  of  which  is  represented 
by  the  formula  C2H2,  by  passing  an  electric  arc  between  carbon 
poles  in  an  atmosphere  of  hydrogen.  Since  that  time,  every 
year  has  witnessed  the  artificial  preparation,  by  purely  chemi- 
cal means,  of  compounds  of  carbon  which  are  found  in  the 
organs  of  plants  and  animals. 

It  hence  appears  that  the  formation  of  the  compounds  of 
carbon  is  not  dependent  upon  the  life  process  ;  that  they  are 
simply  chemical  compounds  governed  by  the  same  laws  that 
govern  other  chemical  compounds  ;  and  the  name,  Organic 
Chemistry,  signifying,  as  it  does,  that  the  compounds  included 
under  it  are  necessarily  related  to  organisms,  is  misleading. 
Organic  chemistry  is  nothing  but  the  Chemistry  of  the  Com- 
pounds of  Carbon.  It  is  not  a  science  independent  of  inorganic 
chemistry,  but  is  just  as  much  a  part  of  chemistry  as  the 
chemistry  of  the  compounds  of  sodium,  or  of  the  compounds 
of  silicon,  etc. 

The  name  Chemistry  of  the  Compounds  of  Carbon  has  been 
objected  to  as  being  too  broad.  Strictly  speaking,  this  title 
includes  the  carbonates,  and  it  is  customary  to  treat  of  these 
widely  distributed  substances  under  the  head  of  Inorganic 
Chemistry.  Most  books  on  Inorganic  Chemistry  also  deal 
with  some  of  the  simpler  compounds  of  carbon,  such  as  the 
oxides,  cyanogen,  marsh  gas,  etc. 


SOURCES    OF    COMPOUNDS  3 

This  objection  is  of  weight  only  as  far  as  the  carbonates 
are  concerned,  and  it  does  not  appear  strong  enough  to  make 
the  introduction  of  a  new  name  necessary.  It  should  be  men- 
tioned, however,  that  the  name  Chemistry  of  the  Hydrocarbons 
and  their  Derivatives  has  been  suggested.  The  exact  signifi- 
cance of  this  name  will  appear  when  the  compounds  with 
which  we  shall  have  to  deal  come  up  for  consideration. 

Sources  of  compounds.  —  The  compounds  of  carbon  are, 
for  the  most  part,  made  in  the  laboratory;  but  in  preparing 
them  we  usually  start  with  a  few  fundamental  compounds 
that  are  formed  by  natural  processes.  A  large  number,  such 
as  the  sugars,  starch,  cellulose,  and  the  alkaloids,  of  which 
morphine,  quinine,  and  nicotine  are  examples,  occur  ready 
formed  in  plants,  but  always  mixed  with  other  substances. 
Others,  such  as  urea,  uric  acid,  albumin,  etc.,  occur  in  animal 
organisms.  Petroleum,  which  has  been  formed  in  nature  by 
processes,  the  exact  nature  of  which  has  not  yet  been  satis- 
factorily explained,  contains  a  large  number  of  compounds  con- 
sisting of  only  carbon  and  hydrogen;  and  these  compounds 
serve  as  the  starting-points  in  the  preparation  of  a  large  num- 
ber of  derivatives.  When  coal  is  heated  for  the  purpose  of 
manufacturing  illuminating  gas,  a  very  complex  mixture  of 
liquid  and  solid  products  is  obtained  as  a  by-product,  known 
as  coal  tar.  This  substance  yields  some  of  the  most  valued 
compounds  of  carbon.  A  larger  number  of  the  compounds  of 
carbon  are  obtained  from  this  than  from  any  other  one  source. 
When  bones  are  heated  in  the  manufacture  of  bone-black,  an 
oil  known  as  bone  oil  is  obtained.  This  also  has  proved  to  be 
the  source  of  a  large  number  of  interesting  compounds.  In 
the  preparation  of  charcoal  by  heating  wood,  the  liquid  prod- 
ucts are  generally  condensed,  and  they  form  the  source  of 
several  important  compounds,  among  which  may  be  mentioned 
wood  spirit  or  methyl  alcohol,  acetone,  and  pyroligneous  or 
acetic  acid. 


4  INTRODUCTION 

Finally,  we  are  dependent  upon  the  process  known  as  fer- 
mentation for  a  number  of  the  most  important  compounds  of 
carbon.  Fermentation,  as  will  be  shown,  is  a  general  term, 
signifying  any  process  in  which  a  change  in  the  composition 
of  a  body  is  effected  by  means  of  minute  animal  or  vegetable 
organisms.  The  best  known  example  of  fermentation  is  that 
of  sugar,  which  gives  rise  to  the  formation  of  ordinary  alcohol. 
Alcohol  in  turn  serves  as  the  starting-point  for  the  preparation 
of  a  large  number  of  compounds. 

Purification  of  the  compounds. — Before  the  natural 
compounds  of  carbon  can  be  studied  chemically,  they  must,  of 
course,  be  freed  from  foreign  substances ;  and  before  the  con- 
stituents of  the  complex  mixtures,  petroleum,  coal  tar,  and  bone 
oil  can  be  studied,  they  must  be  separated  and  purified.  The 
processes  of  separation  and  purification  are,  in  many  cases, 
extremely  difficult.  If  the  substance  is  a  solid,  different 
methods  may  be  used  according  to  the  nature  of  the  substance. 
Crystallization  is  more  frequently  made  use  of  than  any  other 
process.  This  is  well  illustrated,  on  the  large  scale,  in  the 
refining  of  sugar,  which  consists,  essentially,  in  dissolving  the 
sugar  in  water,  filtering  through  bone-black,  which  absorbs 
coloring  matter,  and  then  evaporating  down  to  crystallization. 
When  two  or  more  substances  are  found  together,  they  may,  in 
many  cases,  be  separated  by  what  is  called  fractional  crystalliza- 
tion. This  consists  in  evaporating  the  solution  until,  on  cool- 
ing, a  comparatively  small  part  of  the  substance  is  deposited. 
This  deposit  is  filtered  off,  and  the  solution  further  evaporated  ; 
when  a  second  deposit  is  obtained,  and  so  on  to  the  end.  The 
successive  deposits  thus  obtained  are  then  recrystallized,  each 
separately,  until,  finally,  the  deposits  are  found  to  be  homo- 
geneous. 

The  chief  solvents  used  are  water,  alcohol,  ether,  petroleum 
ether,  benzene,  and  carbon  bisulphide;  alcohol  being  the  one 
most  generally  applicable. 


PUKIFICATION    OF    THE   COMPOUNDS 


in   the  case  of  liquids,  the  process  of  distillation  is  used, 
rJL'he  apparatus  commonly  used  is  illustrated  in  Fig.  1.    • 


B 


Fig.  1. 

The  only  part  of  the  apparatus  that  requires  explana- 
tion is  the  tube  A.  This  is  known  as  the  distilling  tube. 
It  is  simply  a  straight  glass 
tube,  about  16 cm  long  and  12  to 
14 mm  in  diameter,  to  which  is 
attached  a  smaller  branch  some- 
what inclined  downward.  The 
object  of  the  tube  is  to  accom- 
modate a  thermometer  B,  which 
is  so  fixed  by  means  of  a  cork, 
that  it  is  in  the  centre  of  the 
larger  tube,  and  its  bulb  directly 
below  the  opening  of  the  smaller 
branch. 

For  small  quantities  of  liquids, 
the  distilling  flask  is  much  used. 


Fig.  2. 


This  is  a  long-necked,  round 


6  INTRODUCTION 

flask,  with  a  branch  tube  fitted  directly  to  the  neck,  as  shown 
in  Tig.  2.  In  this  apparatus,  the  thermometer  is  fitted  into 
the  neck  of  the  flask  in  the  same  relation  to  the  exit  tube  as 
in  the  larger  apparatus. 

For  the  separation  of  liquids  of  different  boiling-points,  the 
process  of  fractional  or  partial  distillation  is  much  used.  When 
a  mixture  of  two  or  more  liquids  of  different  boiling-points  is 
boiled,  it  will  be  noticed  that  the  boiling-point  gradually  rises 
from  that  of  the  lowest  boiling  substance  to  that  of  the  highest. 
Thus,  ordinary  alcohol  boils  at  78°,  and  water  at  100°.  If  the 
two  are  mixed,  and  the  mixture  distilled,  it  will  be  found  that 
it  begins  to  boil  at  78°,  but  that  very  little  passes  over  at 
this  temperature.  Gradually,  as  the  distillation  proceeds,  the 
temperature  indicated  by  the  thermometer  becomes  higher  and 
higher,  until  at  last  100°  is  reached,  when  all  distils  over. 
Now  the  distillates  obtained  at  the  different  temperatures 
differ  from  each  other  in  composition.  Those  obtained  at  the 
lower  temperatures  are  richer  in  alcohol  than  those  obtained 
at  the  higher  temperatures,  but  none  of  them  contains  pure 
alcohol  or  pure  water.  In  order  to  separate  the  two,  therefore, 
we  must  proceed  as  follows :  A  number  of  clean,  dry  flasks  are 
prepared  for  collecting  the  distillates.  The  boiling  is  begun, 
and  the  point  at  which  the  first  drops  of  the  distillate  appear 
in  the  receiver  is  noted.  That  which  passes  over  while  the 
mercury  rises  through  a  certain  number  of  degrees  (3,  5,  or  10, 
according  to  the  character  of  the  mixture)  is  collected  in  the 
first  flask.  The  receiver  is  then  changed,  without  interruption 
of  the  boiling,  and  that  which  passes  over  while  the  mercury 
rises  through  another  interval  equal  to  the  first  is  collected  in 
the  second  flask.  The  receiver  is  again  changed,  and  a  third 
distillate  collected;  and  so  on,  until  the  liquid  has  all  been  dis- 
tilled over.  It  has  thus  been  separated  into  a  number  of  frac- 
tions, each  of  which  has  passed  over  at  a  different  temperature. 
In  the  case  of  alcohol  and  water,  for  example,  we  might  have 
collected  distillates  from  78°  to  83°,  from  83°  to  88°,  from  88° 


PUKIFICATIOX    OF   THE   COMPOUNDS  7 

to  93°,  from  93°  to  98°,  from  98°  to  100°.  Now  a  clean  dis- 
tilling  flask  is  taken,  and  into  this  the  first  fraction  is  poured. 
This  is  distilled  until  the  thermometer  marks  the  upper  limit 
of  the  original  first  fraction  (83°),  the  new  distillate  being  col- 
lected in  the  flask  which  /  contained  the  first  fraction.  When 
this  upper  limit  is  reached,  the  boiling  is  stopped.  Some  of 
the  liquid  is  left  in  the  distilling  flask.  That  is  to  say,  assum- 
ing that  in  the  first  distillation  the  first  fraction  was  collected 
between  78°  and  83°,  on  boiling  this  fraction  the  second  time 
it  will  not  all  come  over  between  these  points;  when  83°  is 
reached  some  will  be  left  in  the  flask.  The  second  fraction  is 
now  poured  into  the  distilling  flask  through  a  funnel-tube,  and 
the  boiling  is  again  started.  Of  the  second  fraction,  a  portion 
will  pass  over  below  the  point  at  which  it  began  to  boil  (83°) 
when  first  distilled.  Collect  in  the  proper  flask,  and  continue 
the  boiling  until  the  thermometer  marks  the  highest  point  of 
the  fraction  last  introduced,  changing  the  receiver  whenever 
the  indications  of  the  thermometer  require  it.  Now  stop  the 
boiling,  and  pour  in  fraction  No.  3,  and  so  on  until  all  the 
fractions  have  been  subjected  to  a  second  distillation.  On 
examining  the  new  fractions,  it  will  be  found  that  the  liquid 
tends  to  accumulate  in  the  neighborhood  of  certain  points  cor- 
responding to  the  boiling-points  of  the  constituents  of  the 
mixture.  The  distilling  flask  is  now  cleaned,  and  the  whole 
process  repeated.  A  further  separation  is  thus  effected.  By 
continuing  the  distillation  in  this  way,  pure  substances  can,  in 
most  cases,  eventually  be  obtained.  That  the  fractions  are 
pure  can  be  known  by  the  fact  that  the  boiling-points  remain 
constant.  In  some  cases  perfect  separation  cannot  be  effected  by 
means  of  fractional  distillation ;  as,  for  example,  in  the  case  of 
alcohol  and  water.  But  still  it  is  valuable,  even  in  such  cases,  as 
it  makes  it  possible  to  purify  the  substances,  at  least  partially. 
Various  devices  have  been  introduced  for  the  purpose  of  ren- 
dering the  process  of  fractional  distillation  more  rapid  and 
more  efficacious.  One  of  these  that  has  been  extensively  used 


8  INTRODUCTION 

with  good  results  is  the  Hempel  tube.  This  is  "  a  wide  ver- 
tical tube,  filled  with  glass  beads  of  special  construction,  and 
constricted  below  to  prevent  the  beads  falling  out.  A  short, 
narrower,  vertical  with  side  delivery  tube  is  fitted  by  means  of 
an  ordinary  cork  into  the  wide  tube." 1  The  wide  vertical  tube 
is  fitted  into  the  stopper  of  the  distilling  flask. 

The  best  examples  of  distillation  carried  on  on  the  large 
scale  are  those  of  alcohol  and  petroleum.  Probably  the  best 
example  of  fractional  distillation  is  that  of  the  light  oil 
obtained  from  coal  tar. 

This  process  is  carried  on  in  the  so-called  "column  stills,"  of 
which  there  are  several  varieties.  Some  of  them  are  very 
efficient.2 

Experiment  1.  Mix  equal  parts  (about  half  a  litre  of  each)  of  alco- 
hol and  water.  Distil  through  four  or  five  times,  and  notice  the  changes 
in  the  quantities  obtained  in  the  different  fractions. 

Determination  of  the  boiling-point.  —  In  dealing  with 
liquids,  it  often  is  extremely  difficult  to  tell  whether  they  are 
pure  or  not.  The  first  and  most  important  physical  prop- 
erty utilized  for  this  purpose  is  the  boiling  temperature, 
commonly  called  the  boiling-point.  This  is  determined  by 
means  of  an  apparatus,  such  as  is  described  above  as  used  for 
distilling.  The  temperature  noted  on  the  thermometer  when 
the  liquid  is  boiling  is  the  boiling-point.  When  great  accuracy 
is  required,  the  point  observed  directly  must  be  corrected,  in 
consequence  of  the  expansion  of  the  glass  and  the  cooling  of 
that  part  of  the  column  of  mercury  which  is  not  in  the  vapor. 
Full  directions  for  making  these  corrections  can  be  found  in 
larger  books.  A  pure  chemical  compound  always  has  a  con- 
stant boiling-point  under  the  same  barometric  pressure.  On 
the  other  hand,  a  constant  boiling-point  does  not  necessarily 
indicate  a  pure  compound. 

>  See  "  Fractional  Distillation."    By  Sidney  Young  (Macmillan). 


DETERMINATION   OF    THE   MELTING-POINT  9 

Determination  of  the  melting-point.  —  Just  as  the  boil- 
ing-point is  a  very  characteristic  property  of  liquid  bodies,  so 
the  melting-point  is  an  equally  characteristic  property  of  many 
solid  bodies.  If  a  substance  begins  to  melt  at  a  certain  tem- 
perature, and  does  not  melt  completely  at  that  temperature,  it 
is,  in  all  probability,  impure.  By  means  of  the  melting-point 
minute  quantities  of  impurities,  which  might  readily  escape 
detection  by  other  means,  are  often  found.  In  dealing  with 
the  compounds  of  carbon,  determinations  of  melting-points 
are  very  frequently  made.  A  pure  chemical  compound  has 
a  constant  melting-point.  The  determination  is  made  as 
follows :  Small  tubes  are  prepared  by  heating  a  piece  of  ordi- 
nary soft  glass  tubing  of  4mm  to  5mm  diameter,  and  drawing  it 
out.  li  the  parts  are  drawn  apart  about  12cm  to 
15cm,  two  small  tubes  may  be  made  from  the  nar- 
rowed portion  by  melting  together  in  the  middle, 
and  then  filing  off  each  piece  where  it  begins  to 
grow  wider  near  the  large  tube.  These  small 
tubes  must  have  thin  walls,  and  be  of  such  inter- 
nal diameter  that  an  ordinary  pin  can  be  intro- 
duced into  them.  A  small  quantity  of  the  sub- 
stance to  be  tested  is  placed  in  one  of  the  tubes, 
enough  to  make  a  minute  column  of  about  5mm  in 
height.  The  tube  containing  the  substance  is 
fastened  to  a  thermometer  by  means  of  a  small 
rubber  band  or  by  fine  platinum  wire.  The  band 
is  placed  near  the  upper  part  of  the  tube,  and  the 
lower  part  of  the  tube,  containing  the  substance, 
is  placed  against  the  bulb  of  the  thermometer. 
The  thermometer  bulb  is  now  immersed  in  a  small  glass  flask 
containing  pure  sulphuric  acid  (see  Fig.  3).  The  sulphuric 
acid  is  gently  heated  by  a  small  flame  until  the  substance 
melts. 

A  convenient  form  of  apparatus  for  determining  melting-points 
consists  of  a  tube  about  2cm  wide  and  12cm  long,  to  which  a  side 


10  INTRODUCTION 

tube  of  lcm  diameter  is  so  fused  that  it  connects  the  lower  end  of 
the  main  tube  with  the  middle  (see  Fig.  4).  Just  enough 
sulphuric  acid  is  put  into  it  to  close  the  upper 
end  of  the  side  tube.  The  thermometer  is  placed 
so  that  the  bulb  is  midway  between  the  two 
openings  of  the  side  tube.  On  heating  the  tube 
at  the  point  A,  the  sulphuric  acid  begins  to  circu- 
late in  the  apparatus  in  such  a  way  that  it  passes 
downwards  in  the  main  tube.  The  instant  the 
substance  melts  the  temperature  indicated  by  the 
thermometer  is  noted.  This  is  the  melting-point 
It  is  necessary,  however,  to  correct  the  observed 
point  in  the  same  way  as  in  the  case  of  the  boiling-point. 

Experiment  2.  Determine  the  melting-points  of  a  few  substances, 
such  as  urea  and  tartaric  acid.  If  they  do  not  inelt  at  definite  points, 
recrystallize  them  until  they  do.  Note  the  melting-points  observed,  and 
see  how  well  they  agree  with  those  stated  in  the  book.  The  mercury  of 
the  thermometer  should  rise  slowly. 

Analysis.  —  Having  purified  the  compounds,  the  next  step 
is  to  determine  their  composition.  A  comparatively  small 
number  of  the  compounds  ordinarily  met  with  consist  of  car- 
bon and  hydrogen  only ;  the  largest  number  consist  of  these 
two  elements  together  with  oxygen ;  many  contain  carbon, 
hydrogen,  oxygen,  and  nitrogen.  But,  in  the  derivatives  of  the 
fundamental  compounds,  all  other  elements  may  occur.  Thus 
the  hydrogen  may  be  partly  or  wholly  replaced  by  chlorine, 
bromine,  or  iodine,  as  in  the  so-called  substitution-products ; 
and  any  metal  may  occur  in  the  salts  of  the  acids  of  carbon. 
The  estimation  of  carbon  and  hydrogen  is  the  principal  prob- 
lem in  the  analysis  of  the  compounds  of  carbon.  This  is 
effected  by  what  is  known  as  the  combustion  process.  A  known 
weight  of  the  substance  is  completely  oxidized,  the  carbon 
being  thus  converted  into  carbon  dioxide,  and  the  hydrogen 
into  water.  These  two  products  are  collected,  the  water  in 
calcium  chloride,  the  carbon  dioxide  in  a  solution  of  potassium 


ANALYSIS  H 

hydroxide,  and  weighed.  From  the  weights  of  the  products 
the  weights  of  carbon  and  hydrogen  and  the  percentages  are 
calculated.  The  percentages  are  added  together  and  the  sum 
subtracted  from  100.  The  difference  is  the  percentage  of 
oxygen. 

A  detailed  description  of  the  apparatus  and  of  the  method 
of  procedure  need  not  be  given  here,  as  it  can  be  found  in  any 
book  on  analytical  chemistry.  A  brief  description,  however, 
may  not  be  out  of  place.  The  combustion  is  effected  in  a  hard 
glass  tube  which  is  heated  by  means  of  a  gas  furnace  con- 
structed for  the  purpose.  Ordinarily,  the  substance  is  placed 
in  a  narrow  porcelain  or  platinum  vessel,  called  a  boat,  which 
is  introduced  into  the  tube  with  granulated  copper  oxide. 
The  tube  is  then  connected  with  (1)  a  U-tube  filled  with  cal- 
cium chloride ;  (2)  a  set  of  bulbs  containing  a  solution  of 
potassium  hydroxide,  and  constructed  so  as  to  secure  thorough 
contact  of  the  passing  gases  with  the  solution ;  and  (3)  a  small 
U-tube  half  filled  with  solid  potassium  hydroxide,  and  the 
other  half  with  calcium  chloride.  During  the  combustion,  a 
current  of  pure  dry  oxygen  is  passed  through  the  tube ;  and, 
finally,  air  is  passed  until  the  oxygen  is  displaced.  The 
method  at  present  used  was  devised  by  Liebig.  It  has  con- 
tributed very  greatly  to  our  knowledge  of  the  compounds  of 
carbon. 

Two  methods  are  in  common  use  for  the  estimation  of  nitro- 
gen in  carbon  compounds.  The  first  is  known  as  the  absolute 
method.  This  consists  in  oxidizing  the  substance  by  means  of 
copper  oxide;  then  decomposing,  by  means  of  highly-heated 
metallic  copper,  any  oxides  of  nitrogen  which  may  have  been 
formed,  and  collecting  the  nitrogen.  The  volume  of  the  nitro- 
gen thus  obtained  is  measured,  and  its  weight  easily  calculated. 
The  chief  difficulty  in  this  method  consists  in  removing  the 
air  contained  in  the  apparatus  before  the  combustion  is  made. 
The  simplest  way  is  to  pass  pure  carbon  dioxide  through  the 
apparatus  until  the  gas  that  passes  out  is  completely  absorbed 


12  INTRODUCTION 

by  caustic  potash.  The  combustion  is  then  made  by  heating 
the  tube  containing  the  substance  and  copper  oxide  and  a  layer 
of  copper  foil  or  wire  gauze;  and,  finally,  carbon  dioxide  is 
again  passed  through  at  the  end  of  the  operation.  The  only 
three  gases  that  can  be  present,  assuming  that  the  substance 
contained  nothing  but  carbon,  hydrogen,  oxygen,  and  nitro- 
gen, are  carbon  dioxide,  water  vapor,  and  free  nitrogen.  The 
water  vapor  is,  of  course,  condensed,  and  the  carbon  dioxide  is 
absorbed  by  passing  the  gases  through  a  solution  of  potassium 
hydroxide,  leaving  the  nitrogen  thus  alone. 

The  method  now  most  extensively  used  is  that  devised  by 
Kjeldahl.  This  consists  in  heating  the  substance  with  con- 
centrated sulphuric  acid,  potassium  sulphate,  and  a  little  cop- 
per sulphate  or  mercury.  By  this  means  all  the  nitrogen 
contained  in  the  substance  under  examination  is  converted 
into  ammonia,  which,  of  course,  unites  with  the  sulphuric 
acid.  The  ammonia  is  set  free  by  the  addition  of  sodium 
hydroxide,  and  is  estimated  by  absorption  in  standard  acid. 

In  regard  to  the  estimation  of  other  constituents  of  carbon 
compounds,  it  need  only  be  said  that  in  most  cases  it  is  neces- 
sary to  get  rid  of  the  carbon  and  hydrogen  by  some  oxidizing 
process  before  the  estimation  can  be  made.  Thus,  in  estimat- 
ing sulphur,  it  is  customary  to  fuse  the  substance  with  potas- 
sium nitrate  and  hydroxide,  when  the  carbon  and  hydrogen 
are  oxidized,  and  the  sulphur  is  left  in  the  form  of  potassium 
sulphate,  and  can  be  estimated  in  the  usual  way. 

Formula.  —  The  deduction  of  the  formula  of  a  compound 
from  the  results  of  the  analysis  involves  two  steps.  The  first 
is  a  matter  of  simple  calculation.  It  is  assumed  that  students 
who  use  this  book  are  already  familiar  with  the  method  of 
calculating  the  formula  from  the  analytical  results ;  but  an 
example  will,  nevertheless,  be  given.  Suppose  that  the 
analysis  has  shown  that  the  substance  contains  52. 1$  per  cent 
carbon,  13.04  per  cent  hydrogen,  and  34.78  per  cent  oxygen. 


FORMULA  13 


To  get  the  atomic  proportions,  divide  the  figures  representing 
the  percentages  of  the  elements  by  the  corresponding  atomic 
weights.  -  We  have  thus :  — 

Percentage  At.  Wt.        Kelative  No.  of  Atoms 

C  52.18       --       12N     =         4.35       -       2 

H  13.04       -i-         1       =       13.04       -       6 

0  34.78       H-       16       =         2.17       -       1 

That  is  to  say,  accepting  the  atomic  weights,  12  for  carbon  and 
16  for  oxygen,  the  simplest  figures  representing  the  number  of 
atoms  of  the  three  elements  in  the  compound  are  2  for  carbon, 
6  for  hydrogen,  and  1  for  oxygen.  According  to  this,  the 
simplest  formula  that  can  be  assigned  to  a  substance  giving 
the  above  results  on  analysis  is  C2H60.  But  •  the  formula 
C4H1202  is  equally  in  accordance  with  the  analytical  results, 
and  we  can  only  decide  between  the  two  by  determining  the 
molecular  weight.  This  is  done  by  determining  the  specific 
gravity  of  the  substance  in  the  form  of  vapor.  It  is  assumed 
that  the  student,  who  has  already  studied  the  elements  of 
inorganic  chemistry,  is  familiar  with  the  methods  used  in 
determining  the  specific  gravity  of  vapors,  and  with  the  con- 
nection that  exists  between  the  specific  gravity  and  the  molec- 
ular weight  of  the  compound.  A  few  statements  in  regard 
to  the  connection  will,  however,  be  made  here,  in  order  to 
impress  upon  the  mind  of  the  student  its  fundamental 
importance. 

Every  chemical  formula  is  intended  to  represent  the  relative 
weight  of  the  molecule  of  a  compound  and  the  composition  of 
the  molecule.  Our  conception  of  the  relative  weight  of  the 
molecule  is  based  almost  exclusively  on  Avogadro's  law,  accord- 
ing to  which  equal  volumes  of  all  gases  under  the  same  condi- 
tions of  temperature  and  pressure  contain  the  same  number  of 
molecules.  Hence,  by  comparing  the  weights  of  equal  volumes 
of  compounds  in  the  form  of  gas  or  vapor,  we  obtain  figures 
which  bear  to  one  another  the  same  relations  as  the  weights  of 


14  INTRODUCTION 

the  molecules.  The  figures  called  the  specific  gravities  express 
the  relations  between  the  weights  of  equal  volumes.  In  the 
case  of  gases,  air  is  generally  taken  as  the  standard,  and  the 
weights  of  other  gases  are  compared  with  this  standard.  Thus, 
when  we  say  that  the  specific  gravity  of  a  gas  is  0.918,  we  mean 
that  if  the  weight  of  any  volume  of  air  is  1  gram,  that  of  the 
same  volume  of  the  other  gas  measured  under  the  same  condi- 
tions of  temperature  and  pressure  is  0.918  gram.  Knowing 
the  molecular  weight  of  any  gaseous  compound  it  is  an  easy 
matter  to  deduce  the  molecular  weights  of  all  other  gaseous 
compounds  or  of  those  that  can  be  converted  into  vapor  without 
decomposition.  The  ratio  between  the  molecular  weight,  M, 
and  specific  gravity,  d,  is  the  same  in  all  cases,  that  is  to  say, 
if  M  represents  the  molecular  weight  of  any  gas  whose  specific 
gravity  is  represented  by  d,  and  Ml  the  molecular  weight  of 
any  other  gas  whose  specific  gravity  is  dl}  then 


or  —  =  a  constant. 
d  , 

This  constant  has  been  found  to  be  about  28.87.  Hence,  in 
any  case,  the  molecular  weight,  M,  is  equal  to  the  specific 
gravity,  d,  multiplied  by  28.87,  or 

M=dx  28.87. 

Thus  to  illustrate  by  means  of  the  compound  whose  atomic  re- 
lations have  been  found  by  analysis  to  be  represented  by  the 
formulas  C2H60,  C4H1202,  C6HJ803,  or  some  higher  multiple  of 
C2H60.  Suppose  that,  when  this  compound  is  converted  into 
vapor  and  the  specific  gravity  of  the  vapor  determined,  it 
should  be  found  to  be  1.6. 

M  (the  unknown  molecular  weight)  =  1.6  X  28.87  =  46.2. 


STRUCTURAL   FORMULA  15 

If  the  formula  of  the  compound  is  C2H60,  the  molecular  weight, 
being  the  sum  of  the  weights  of  the  constituent  atoms,  is 

2x12  +  6x1  +  16  =  46, 

which  agrees  with  the  figure  deduced  from  the  specific  gravity. 
It  therefore  follows  that  the  formula  C2H60  is  correct. 

The  molecular  weight  of  an  acid  can  be  determined  by 
analyzing  its  salts.  To  illustrate  this  take  acetic  acid.  This 
is  a  monobasic  acid,  that  is  to  say  it  gives  but  one  silver  salt 
and  contains  but  one  replaceable  hydrogen  atom.  Now  analysis 
of  acetic  acid  shows  that  it  has  the  composition  represented  by 
the  formulas  CH20,  C2H402,  C3H603,  etc.  The  analysis  of  the 
silver  salt  shows  that  it  must  be  represented  by  the  formula 
C2H302Ag  and  not  CHOAg,  and  hence  the  molecular  formula 
of  acetic  acid  is  C2H402  and  not  CH20. 

By  determining  the  boiling-points  and  by  determining  the 
freezing-points  of  solutions  it  is  possible  to  determine  the 
molecular  weights  of  many  compounds  of  carbon.  This  is 
due  to  the  fact  that,  in  the  case  of  any  given  solvent,  weights 
of  different  compounds  of  carbon  bearing  to  one  another  the 
same  relation  as  their  molecular  weights  cause  the  same  ele- 
vation of  the  boiling-point  of  the  liquid  and  the  same  depres- 
sion of  the  freezing-point.  The  details  of  these  methods  cannot 
be  given  here. 

Structural  formula.  —  The  formulas  C2H60,  C2H402,  C3H8, 
etc.,  tell  us  simply  the  composition  of  the  three  compounds 
represented,  and  tell  us  also  the  weights  of  their  molecules. 
In  studying  the  chemical  conduct  of  these  compounds,  their 
decompositions,  and  the  modes  of  preparing  them,  we  become 
familiar  with  many  facts  which  it  is  desirable  to  represent  by 
means  of  the  formulas.  Thus,  for  example,  but  one  of  the  four 
atoms  of  hydrogen  represented  in  the  formula  of  acetic  acid, 
C2H402,  can  be  replaced  by  metals.  It  plainly  differs  from  the 
three  remaining  atoms,  and  it  is  natural  to  conclude  that  it  is 
held  in  the  molecule  in  some  way  differently  from  the  other 


16  INTRODUCTION 

three.  We  may,  therefore,  write  the  formula  C2H302.H,  which 
is  intended  to  call  attention  to  this  difference.  By  further 
study  of  acetic  acid,  we  find  that  the  particular  hydrogen, 
which  gives  to  it  acid  properties,  and  which,  in  the  above 
formula,  is  written  by  itself,  is  intimately  associated  with 
oxygen.  It  can  be  removed  with  oxygen  by  simple  reactions, 
and  the  place  of  both  taken  by  one  atom  of  some  other  ele- 
ment, as,  for  example,  chlorine.  Thus,  when  acetic  acid  is 
treated  with  phosphorus  trichloride,  PC13,  it  is  converted  into 
acetyl  chloride,  C2H3OC1.  The  result  of  the  action  is  the 
direct  substitution  of  one  atom  of  chlorine  for  one  atom  of 
hydrogen  and  one  atom  of  oxygen  in  acetic  acid,  a  fact  which 
points  to  an  intimate  connection  between  the  hydrogen  and 
oxygen  in  the  acid.  Further,  when  acetyl  chloride  is  heated 
with  water,  acetic  acid  is  regenerated,  hydrogen  and  oxygen 
from  the  water  entering  into  the  place  occupied  by  the  chlo- 
rine, as  represented  in  this  equation  :  — 

C2H3OC1  +  H20  =  C2H402+HC1. 

From  facts  of  this  kind  the  conclusion  is  drawn  that  in  acetic 
acid  hydrogen  and  oxygen  are  connected;  or,  as  it  is  said,  linked 
together;  and  this  conclusion  is  represented  in  chemical  lan- 
guage by  the  formula  C2H3O.OH,  which  may  serve  as  a  simple 
illustration  of  what  are  called  structural  or  constitutional  for- 
mulas. In  all  compounds  the  attempt  is  made,  by  means  of  a 
thorough  study  of  the  conduct  of  the  compounds,  to  trace  out 
the  connections  existing  between  the  constituent  atoms.  When 
this  can  be  done  for  all  the  atoms  contained  in  a  molecule,  the 
structure  or  constitution  of  the  molecule  or  of  the  compound  is 
said  to  be  determined.  The  structural  formulas  which  have 
been  determined  by  proper  methods  have  proved  of  much  value 
in  dealing  with  chemical  reactions,  as  they  enable  the  chemist 
who  understands  the  language  in  which  they  are  written  to  see 
relations  which  might  easily  escape  his  attention  without  their 
aid.  In  order  to  understand  them,  however,  the  student  must 


CLASSIFICATION    OF    COMPOUNDS    OF   CARBON          17 

have  a  knowledge  of  the  reactions  upon  which  they  are  based  > 
and  he  is  warned  not  to  accept  any  chemical  formula  unless  he 
can  see  the  reasons  for  accepting  it.  He  should  ask  the  ques- 
tion, upon  what  facts  is  it  based  ?  whenever  a  formula  is  pre- 
sented for  the  first  time.  If  he  does  this  conscientiously,  he 
will  soon  be  able  to  use  the  language  intelligently,  and  the 
beauty  of  the  relations  that  exist  between  the  large  number 
of  compounds  of  carbon  will  be  revealed  to  him.  If  he  does 
not,  his  mind  will  soon  be  in  a  hopeless  muddle,  and  what  he 
learns  will  be  of  little  value.  For  the  beginner,  this  advice  is 
of  vital  importance :  Study  with  great  care  the  reactions  of  com- 
pounds; study  /j*>  vg.ptli.nrfa  nf  n^^ng  tttonm.^  civni  the  decomposi- 
tions  which  then  undergo.  T^lie  formulas  are  but  the  condensed 
expressions  of  the  conclusions  which  are  drawn  from  the  reactions. 

General  principle  of  classification  of  the  compounds 
of  carbon. — In  considering  the  elements  and  compounds  in- 
cluded under  the  head  of  Inorganic  Chemistry,  the  fundamental 
substances  are,  of  course,  the  elements.  The  properties  of  the 
elements  enable  us  to  separate  them,'  for  study,  into  a  number 
of  groups;  as,  for  example,  the  chlorine  group,  including 
bromine,  iodine,  and  fluorine ;  the  oxygen  group,  in  which 
are  included  sulphur,  selenium,  and  tellurium.  To  recall  the 
method  generally  adopted,  let  us  take  the  chlorine  group. 
In  studying  the  members  of  this  group,  there  is  found  great 
similarity  in  their  properties.  Their  hydrogen  compounds 
next  present  themselves,  and  here  the  same  similarity  is  met 
with.  Then,  in  turn,  the  oxygen  and  the  oxygen  and  hydrogen 
compounds  are  considered,  and  again  the  resemblances  in 
properties  between  the  corresponding  compounds  of  chlorine, 
bromine,  and  iodine  are  met  with.  We  thus  have  groups  of 
elements,  and  of  the  derivatives  of  these  elements,  as, — 

Cl  C1H  C103H 

Br  BrH  Br03H 

I  IH  I03H,  etc. 


18  INTRODUCTION 

Of  course,  the  chlorine  group  is  quite  distinct  from  the  oxygen 
group  and  from  all  other  groups;  and  each  member  of  the 
chlorine  group  is,  at  least  so  far  as  we  know,  quite  independent 
of  the  other  members.  We  cannot  make  a  bromine  compound 
from  a  chlorine  compound,  nor  a  chlorine  compound  from  a 
bromine  compound,  without  directly  substituting  the  one  ele- 
ment for  the  other. 

Now,  when  we  come  to  study  the  compounds  of  carbon,  we 
shall  find  that  the  same  general  principle  of  classification  is 
made  use  of ;  only,  in  consequence  of  the  peculiarities  of  the 
compounds,  the  system  can  be  carried  out  much  more  perfectly ; 
the  members  of  the  same  group  can  be  transformed  one  into 
the  other,  and  it  is  also  possible  to  pass  from  one  group  to 
another  by  means  of  comparatively  simple  reactions. 

The  simplest  compounds  of  carbon  are  those  which  contain 
only  hydrogen  and  carbon,  or  the  hydrocarbons.  All  the  other 
compounds  may  be  regarded  as  derivatives  of  the  hydrocarbons. 
To  begin  with,  there  are  several  groups  or  series  of  hydrocar- 
bons, which  correspond  somewhat  to  the  different  groups  of 
elements.  The  members  of  one  and  the  same  series  of  hydro- 
carbons, resemble  one  another  more  closely  than  the  members  of 
one  and  the  same  series  of  elements.  Although  we  have  indica- 
tions of  the  existence  of  more  than  ten  series  of  these  hydrocar- 
bons, only  three  or  four  of  the  series  are  at  all  well  known,  and 
of  these  but  two  include  more  than  two  or  three  members  that 
need  to  be  treated  of  in  this  book. 

Starting  with  any  series  of  hydrocarbons,  several  classes  of 
derivatives  can  be  obtained  by  treating  the  fundamental  com- 
pounds with  different  reagents.  The  chief  classes,  of  these 
derivatives  are :  (1)  those  containing  halogens ;  (2)  those  con- 
taining oxygen,  among  which  are  the  acids,  alcohols,  ethers,  etc. ; 
(3)  those  containing  sulphur ;  and  (4)  those  containing  nitrogen. 
Corresponding  to  every  hydrocarbon,  then,  we  may  expect  to  find 
representatives  of  these  different  classes  of  derivatives.  But  the 
relations  existing  between  any  hydrocarbon  and  its  derivatives 


CLASSIFICATION   OP   COMPOUNDS   OF   CAEBON          19 

are  the  same  as  those  existing  between  any  other  hydrocarbon 
and  its  derivatives.  Hence,  if  we  know  what  derivatives  one 
hydrocarbon  can  yield,  we  know  what  derivatives  we  may  expect 
to  find  in  the  case  of  every  other  hydrocarbon.  The  student 
who,  for  the  first  time,  undertakes  the  study  of  the  chemistry 
of  the  compounds,  is  apt  to  feel  overwhelmed  by  the  enormous 
number  of  compounds  described  in  the  book  or  by  the  lecturer. 
This  large  number  is  really  not  a  serious  matter.  No  one  is 
expected  to  become  acquainted  with  every  compound.  A  great 
many  of  these  need  only  be  referred  to  for  the  purpose  of  indicat- 
ing the  extent  to  which  the  series  to  which  they  belong  have  been 
developed.  In  general,  the  members  of  any  series  so  closely 
resemble  one  another,  that,  if  we  understand  the  simpler  mem- 
bers, we  have  a  fair  knowledge  of  the  more  complicated  members. 

It  is  proposed,  in  this  book,  to  treat  only  of  the  more  im- 
portant compounds  and  the  more  important  reactions,  the 
object  being  rather  to  give  a  clear,  general  notion  of  the  subject 
than  detailed  information  regarding  particular  compounds. 
Should  the  student  desire  more  specific  information  concerning 
the  properties  of  any  of  the  compounds  mentioned,  he  can 
easily  find  it  in  some  larger  book.  It  will,  however,  hardly 
be  profitable  for  him,  at  the  outset,  to  burden  his  mind  with 
details.  He  may  thereby  sacrifice  the  general  view,  which  it 
is  so  important  he  should  gain  as  quickly  as  possible. 

The  plan  that  will  be  followed  is  briefly  this :  Of  the  first 
series  of  hydrocarbons  two  members  will  be  treated  of.  Then 
the  derivatives  of  these  two  will  be  taken  up.  These  deriva- 
tives will  serve  admirably  as  representatives  of  the  correspond- 
ing derivatives  of  other  hydrocarbons  of  the  same  series,  and  of 
other  series.  Their  characteristics  and  their  relations  to  the 
hydrocarbons  will  be  dwelt  upon,  as  well  as  their  relations  to 
each  other.  Thus,  by  a  comparatively  close  study  of  two  hydro- 
carbons and  their  derivatives,  we  may  acquire  a  knowledge  of  the 
principal  classes  of  the  compounds  of  carbon.  After  these  typical 
derivatives  have  been  discussed,  the  entire  series  of  hydrocar- 


20  INTRODUCTION 

bons  will  be  taken  up  briefly,  only  such,  facts  being  dealt  with 
at  all  fully  as  are  not  illustrated  by  the  first  two  members. 

After  the  first  series  has  been  studied  in  this  way,  and  a 
clear  idea  of  the  relations  between  the  various  classes  has  beer 
obtained,  a  second  series  will  be  taken  up  and  treated  in  a 
similar  way,  and  so  on.  But,  as  already  stated,  only  a  few 
of  the  series  require  much  attention  at  the  beginning.  The 
first  series  that  will  be  used  for  the  purpose  of  illustrating  the 
general  principles  is  one  of  the  two  most  important  series,  and 
of  the  only  two  that  need  be  taken  up  at  all  fully  at  present. 


CHAPTER  II 
METHANE  AND  ETHANE  —  HOMOLOGOUS  SERIES 

IF  we  were  to  study  all  the  hydrocarbons  known,  and  were 
then  to  arrange  them  in  groups  according  to  their  properties, 
we  should  find  that  a  large  number  of  them  resemble  marsh  gas 
in  their  general  conduct.  Some  of  the  points  of  resemblance 
are  these :  They  are  very  stable,  resisting  with  marked  power 
the  action  of  most  reagents ;  and  nothing  can  be  added  to  them 
directly,  —  if  any  change  takes  place  in  them,  hydrogen  is  first 
given  up.  On  arranging  these  substances  according  to  the 
number  of  carbon  atoms  contained  in  them,  we  have  a  remark- 
able series,  the  first  six  members  of  which,  together  with  their 
formulas,  are  included  in  the  subjoined  table :  — 

Methane  (or  Marsh  Gas)     ....  CH4 

Ethane C2H4 

Propane C3H8 

Butane C4H10 

Pentane CgH^ 

Hexane .     .  C6H14 

On  examining  the  formulas  given,  it  will  be  seen  that  the  dif- 
ference in  composition  between  any  two  consecutive  members 
is  represented  by  CH2.  Thus,  adding  CH2  to  marsh  gas,  CH4, 
we  get  ethane,  C2H6 ;  adding  CH2  to  C2H6,  we  get  C3H8,  and  so 
on,  at  each  successive  step.  Any  series  of  this  kind,  in  which 
the  successive  members  increase  in  complexity  by  CH2,  is 
called  an  homologous  series. 

Just  as  the  members  of  an  homologous  series  of  hydrocarbons 
differ  from  one  another  by  CH2,  or  some  multiple  of  it,  so 

21 


22  METHANE   AND   ETHANE 

also  the  members  of  any  class  of  derivatives  of  these  hydro- 
carbons differ  from  one  another  in  the  same  way,  and  form 
homologous  series.  Thus,  running  parallel  to  the  hydrocarbons 
mentioned  above,  there  are  two  homologous  series  of  oxygen 
derivatives,  as  indicated  below :  — 

CH4  -CH4Q_  -CH202 
C2H6  -  CsHiQ1!-  G2H402 
C3H8  —  C3H80  —  C3H602 
C4H10  —  C4H100  —  C4H802 
CsH12  —  C5H120  —  C5H1002 
C6H14  —  C6H140  —  CgH^Oz 

The  relation  observed  between  the  members  of  the  homologous 
series  mentioned  is  by  no  means  a  peculiarity  of  the  marsh 
gas  series  of  hydrocarbons  and  of  their  derivatives,  but  is 
observed  in  the  case  of  all  other  series  of  hydrocarbons  and 
their  derivatives. 

Strictly  speaking,  there  is  perhaps  no  analogy  for  this  re- 
markable fact  among  the  elements  and  their  compounds,  yet 
facts  which  suggest  analogy  are  known.  Consider,  for  example, 
the  chlorine  series.  We  have 

Chlorine,  with  the  atomic  weight,  35.4. 
Bromine,    ,    "  "  "       80. 

Iodine,  "  «  "     127. 

As  is  well  known,  the  difference  between  the  atomic  weights  of 
chlorine  and  bromine  is  approximately  equal  to  the  difference 
between  those  of  bromine  and  iodine.  In  other  words,  there  is 
a  regular  increase  in  complexity  as  we  pass  from  chlorine  to 
iodine.  Or,  at  least,  there  is  a  regular  increase  in  the  atomic 
weights  of  these  similar  elements,  just  as  there  is  a  regular 
increase  in  the  molecular  weights  of  the  similar  members  of  an 
homologous  series.  While,  however,  a  satisfactory  hypothesis 
has  been  offered  to  account  for  the  latter  fact,  and  experi- 


METHANE  AND   ETHANE  23 

mental  evidence  is  strongly  in  favor  of  the  hypothesis,  no  satis- 
factory explanation  of  the  former  has  been  offered ;  or  rather 
no  satisfactory  experimental  evidence  has  been  furnished  in 
favor  of  the  various  hypotheses  which  from  time  to  time  have 
been  put  forward  to  account  for  the  similarity  between  members 
of  the  same  group  of  elements. 

The  view  at  present  held  in  regard  to  the  nature  of  homology 
is  founded,  primarily,  upon  the  idea  that  carbon  is  quadrivalent. 
If  carbon  is  quadrivalent,  it  of  course  follows  that  the  com- 
pound, marsh  gas,  CH^  is  saturated;  that  is,  the  molecule 
cannot  take  up  anything  without  losing  hydrogen.  In  order, 
therefore,  that  we  may  get  a  compound  containing  two  atoms 
of  carbon  in  the  molecule,  some  of  the  hydrogen  must  first  be 
given  up.  With  our  present  views,  we  cannot  conceive  of  union 
taking  place  directly  between  the  molecules  CH4  and  CH4,  but 
we  can  conceive  of  union  taking  place  between  the  molecules 
CH3  and  CH3,  to  form  a  molecule  C2H6,  which  in  turn  is  satu- 
rated. Eepresenting  graphically  what  is  believed  to  take 
place,  we  have,  first,  marsh  gas,  which  we  may  represent  thus, 
H 

H-C— H.     If  this  loses  one  atom  of  hydrogen,  we  have  the 

I  H 

H  I 

unsaturated   residue  H-C -,  which  is  capable  of  uniting  with 

H 
another  residue  of  the  same  kind  to  form  the  more  complex 

H    H 

I     'I 
molecule  H— C-C— H,  or  C2H6,  which  is   believed   to  express 

I      I 

H   H 

the  relation  existing  between  marsh  gas,  CH4,  and  ethane,  C2H6, 
or  between  any  two  adjoining  members  of  an  homologous  series. 
The  evidence  in  favor  of  this  view  will  be  presented  when  the 
reactions  by  means  of  which  the  hydrocarbons  are  made 
are  discussed.  The  explanation  offered,  and  now  generally 


24  METHANE  AND   ETHANE 

accepted,  involves  the  idea  that  carbon  atoms  have  the  power 

Qf  Uniting  with  ftaftl^  Qffhftr.__  AndT  a.a  t.hp.  p.yp1a.na±Tnin'?nv  the 

relation  between  the  first  and  second  members  is,  in  principle, 
the  same  as  for  the  relation  between  the  second  and  third,  the 
third  and  fourth,  etc.,  it  appears  that  this  power  of  carbon  atoms 
to  unite  with  one  another  is  very  extensive.  It  is  to  the  power 
which  carbon  possesses  of  forming  homologous  series,  .or  to  the 
power  of  the  atoms  of  carbon  to  unite  with  each  other,  that  we 
owe  the  large  number  of  compounds  of  this  element. 

Methane,  marsh  gas,  fire  damp,  CH4.  —  This  hydro- 
carbon is  found  rising  from  pools  of  stagnant  water  in  marshy 
districts.  If  a  bottle  is  rilled  with  water  and  inverted  with  a 
funnel  in  its  neck  in  such  a  pool/some  of  the  gas  can  be  col- 
lected by  holding  the  funnel  o\qfcthe  bubbles  rising  from  the 
bottom.  It  is  also  found  in  large  quantities  mixed  with  air, 
in  coal  mines,  and  sometimes  issues  from  the  earth,  together 
with  other  gases,  in  the  neighborhood  of  petroleum  wells.  It 
is  a  constituent  of  natural  gas. 

It  can  be  prepared 

(1)  By  treating  aluminium  carbide,  ("3A14,  with  water:  — 

C3A14  +  12  ILO  =  3  CH4  -f  1  Al  (OH)3. 

(2)  By  passing  hydrogen  over  a  mixture  of  nickel  and  carbon. 

(3)  By  reduction  of  carbon  monoxide  or  dioxide  with  calcium 
hydride. 

(4)  By  heating  finely-divided  carbon  with  calcium  hydride. 

(5)  By  direct  combination  of  carbon  and  hydrogen  at  1150°. 
It  is  formed,  as  its  occurrence  in  marshes  indicates,  by  the 

decomposition  of  organic  matter  under  water.  In  pure  condi- 
tion it  is  made  most  readily  by  heating  a  mixture  of  sodium 
acetate  and  soda-lime :  — 

NaC2H302  +  NaOH  =  CH4  -f-  Na.C03. 

It  will  be  shown  hereafter  thafc  ,mos^  acids  of  carbon  break  up 
in  a  similar  way,  yielding  a  hydrocarbon  and  a  carbonate. 


METHANE   (MARSH   GAS,    FIEE   DAMP)  25 

Properties.  Marsh  gas  is  colorless  and  inodorous.  It  is 
slightly  soluble  in  water,  but  not  so  much  so  as  to  prevent  its 
collection  over  water.  It  burns.  Its  mixture  with  air  often 
explodes  when  a  flame  is  applied.  This  mixture  is  the  cause 
of  some  of  the  explosions  in  coal  mines.  In  ordinary  language 
it  is  known  as  fire  damp.  The  explosion  is  due  to  the  rapid 
combustion  of  the  marsh  gas.  The  products  are  carbon  dioxide 
and  water:  — 


Carbon  dioxide  is  known  to  the  miner  as  choke  damp. 

The  most  common  cause  of  explosions  in  coal  mines  is  coal 
dust.  The  explosion  is,  in  fact,  an  extremely  rapid  combustion 
giving  carbon  monoxide  and  dioxide. 

Experiment  3.  Make  marsh  gas.  Dehydrate  some  sodium  acetate 
by  heating  it  in  a  porcelain  dish  on  wire  gauze  over  a  small  flame.  Use 
10s  of  sodium  acetate  and  20s  of  powdered  soda-lime.  Collect  the  gas 
over  water.  Burn  some  as  it  escapes  from  a  jet.  In  small  quantities  it 
does  not  readily  explode  with  air. 

Reagents,  in  general,  do  not  act  readily  upon  marsh  gas. 
Chlorine  in  diffused  daylight  gradually  takes  the  place  of  the 
hydrogen,  forming  a  series  of  compounds  which  will  be  treated 
of  under  the  head  of  the  halogen  derivatives  of  methane.  The 
simplest  of  them  has  the  composition  represented  by  the 
formula  CH3C1,  and  is  known  as  chlor-methane  or  methyl 
chloride. 


Ethane,  C2H6.  —  Ethane  rises  from  the  earth  from  some  of 
the  gas  wells  in  the  regions  in  which  petroleum  occurs.  It  is 
also  found  dissolved  in  crude  petroleum. 

It  can  be  made  from  methane  by  introducing  a  halogen  and 
making  a  compound  like  chlor-methane,  CH3C1.  As  the  cor- 
responding iodine  derivative  is  less  volatile,  it  is  used.  This 
iodo-methane,  CH3I,  is  treated  with  zinc  or  sodium  in  some 


26  METHANE   AND   ETHANE 

neutral  medium,  as,  for  example,  anhydrous  ether.  The  reac- 
tion which  takes  place  is  represented  thus  :  — 

CH3I  +  CH3I  +  2  Na  =  C2H6  +  2  Nal. 

This  method  of  building  up  more  complex  from  simpler  hydro- 
carbons has  been  used  extensively  ;  and  it  is  well  adapted  to 
showing  the  relations  between  the  substances  formed  and  the 
simpler  ones  from  which  they  are  made. 

An  operation  of  the  kind  involved  'in  the  above-mentioned 
preparation  of  ethane  is  called  a  synthesis.      The   essential 

featurejrf    the    Synthesis    is   t>»A   -Fnnmnf^n   rvP   p.  mnrp.  p.omplpy 

aubsfo.nce  frpm  simpler  ones.  Our  knowledge  of  the  structure 
of  the  compounds  of  carbon  is  largely  dependent  upon  the  use 
of  various  methods  of  synthesis.  For  example,  in  the  case 
under  consideration,  the  synthesis  gives  us  at  once  a  clear  view 
of  the  relations  between  ethane  and  methane,  and  also  suggests 
that  homology  may  be  due  to  similar  relations  between  the 
successive  members  of  the  series,  —  a  view  which  is  fully  con- 
firmed by  the  synthetical  preparation  of  the  higher  members. 
A  similar  method  of  synthesis  has  been  used  in  the  preparation 
of  tetrathionic  acid  from  sodium  thiosulphate.  The  action  is 
represented  thus  :  — 

>  + 


Two  mol.  sodium  Sodium  tetra- 

thiosulphate  thionate 


CHAPTER   III 
HALOGEN  DERIVATIVES  OF  METHANE  AND  ETHANE 

Substitution.  —  When  methane  and  chlorine  are  brought 
together  in  diffused  daylight,  action  takes  place  gradually ; 
hydrochloric  acid  gas  is  given  off,  and  one  or  more  products 
are  obtained,  according  to  the  length  of  time  the  action  con- 
tinues. The  products  have  been  studied  carefully,  and  four 
have  been  isolated.  The  composition  of  these  products  is  rep- 
resented by  the  formulas  CH3C1,  CH,C12,  CHC18,  and  CC14. 
We  see  thus  that  the  action  of  chlorine  consists  in  replacing, 
step  by  step,  the  hydrogen  of  the  hydrocarbon.  The  action  is 
represented  by  the  four  equations :  — 

(1)  CH4       +  C12  =  CH3C1  4-  HC1 ; 

(2)  CH3C1  +  C12  =  CH2C12  + HC1; 

(3)  CH2C12  +  C12  =  CHC13  +  HC1; 

(4)  CHC13  +  C12  =  CC14      +  HC1. 

This  replacement  of  hydrogen  by  chlorine  is  an  example  of 
what  is  known  as  substitution.  We  shall  find  that  most  hydro- 
carbons are  susceptible  to  the  influence  of  the  halogens  and 
a  number  of  other  reagents,  such  as  nitric  acid,  sulphuric 
acid,  etc.,  and  that  thus  a  large  number  of  derivatives  can  be 
made,  differing  from  the  hydrocarbons  in  that  they  contain 
one  or  more  halogen  atoms  or  complex  groups  in  the  place 
of  the  same  number  of  hydrogen  atoms.  It  must  be  borne  in 
mind  that  the  mere  fact  that  chlorine,  in  acting  upon  marsh 
gas,  is  substituted  for  an  equivalent  quantity  of  hydrogen,  does 
not  prove  that  the  chlorine  in  the  product  occupies  the  same 
place  that  the  replaced  hydrogen  did.  Nevertheless,  a  careful 
study  of  all  the  facts  regarding  the  products  thus  formed  has 
led  to  the  belief  that  the  substituting  atom  or  residue  does 

27 


28  DERIVATIVES   OF   METHANE   AND  ETHANE 

occupy  the  same  place,  or  bear  the  same  relation  to  the  carbon 
atom  as  the  hydrogen  did. 

The  name  substitution-products  properly  includes  all  products 
made  from  the  hydrocarbons,  or  from  other  carbon  compounds, 
by  the  substitution  process.  The  principal  ones  are  those 
formed  by  the  action  of  the  halogens,  or  the  halogen  substitution- 
products;  those  formed  by  the  action  of  nitric  acid,  or  the 
nitro-substitution-products  ;  and  those  formed  by  the  action  of 
sulphuric  acid,  or  the  sulphonic  acids.  The  last  are,  however, 
not  commonly  called  substitution-products. 

Chlor-methane,  methyl  chloride,  CH3C1. 

Brom-methane,  methyl  bromide,  CH3Br. 

lodo-methane,   methyl  iodide,      CH3I. 

The  chlorine  and  bromine  products  can  be  made  by  treating 
methane  with  the  corresponding  element.  They  can  be  most 
easily  made  by  treating  methyl  alcohol  with  the  corresponding 
hydrogen  acids :  — 

CH40  +  HC1  =  CH3C1  +  H20. 

Methyl  alcohol  •Chlor-methane 

Di-iodo-methane,  methylene  iodide,  CH2l2- — This  sub- 
stance is  the  principal  halogen  derivative  of  methane  containing 
two  halogen  atoms.  It  is  made  from  iodoform  or  tri-iodo- 
methane,  CHI3,  by  treating  it  with  hydriodic  acid,  the  latter 
acting  as  a  reducing  agent :  — 

CHI3  +  HI  =  CH2I2-f  I2. 

As  will  be  seen,  this  is  a  case  of  reverse  substitution;  in  other 
words,  the  action  is  the  opposite  of  that  described  above  as 
substitution.  Methylene  iodide  is  a  liquid  that  boils  at  180°, 
and  has  the  specific  gravity  3.342. 

Chloroform,  CHC13.  i      The  best  known  and  most  exten- 

Bromoform,  CHBr3. 1  sively  used  of  these  three  derivatives 

Iodoform,      CHI3.    J  is    chloroform    or    tri-chlor-methane. 

It  is  made  by  treating  alcohol  or  acetone  with  "bleaching 


DI-IODOETHANE  29 

powder."  The  action  is  deep-seated,  involving  at  least  three 
different  stages.  It  will  be  treated  of  more  fully  under  the 
head  of  chloral  (which  see).  Chloroform  is  a  heavy  liquid  of 
specific  gravity  1.526.  It  has  an  ethereal  odor,  and  a  some- 
what sweet  taste.  It  is  scarcely  soluble  in  water.  It  boils  at 
61.2°.  It  is  one  of  the  most  valuable  anaesthetics,  though 
there  is  some  danger  attending  its  use. 

Experiment  4.  Mix  550s  bleaching  powder  and  1£  litres  water  in  a 
3-litre  flask.  Add  33s  alcohol  of  sp.  gr.  0.834.  Heat  gently  on  a  water- 
bath  until  action  begins.  A  mixture  of  alcohol,  water,  and  chloroform 
will  distil  over.  Add  water,  and  remove  the  chloroform  by  means  of  a 
pipette.  Add  calcium  chloride  to  the  chloroform,  and,  after  standing, 
distil  on  a  water-bath. 

lodoform,  which  is  used  extensively  in  surgery,  is  made  by 
bringing  together  alcohol,  an  alkali,  and  iodine.  It  is  a  solid 
substance,  soluble  in  alcohol  and  ether,  but  insoluble  in  water. 
It  crystallizes  in  delicate,  six-sided,  yellow  plates.  Melting- 
point,  119°. 

Experiment  5.  Dissolve  20s  crystallized  sodium  carbonate  in  1008 
water.  Pour  10s  alcohol  into  the  solution,  and,  after  heating  to  60° 
to  80°,  gradually  add  10s  iodine.  The  iodoform  separates  from  the  solution. 

Tetra-chlor-methane,  CC14,  is  made  by  treating  carbon  bisul- 
phide with  chlorine,  and  by  treating  chloroform  with  iodine 
chloride,  IC1.  It  is  manufactured  on  a  large  scale  and  used 
as  a  solvent  for  fats  and  as  a  fire  extinguisher  (pyrene). 

Equivalence  of  the  hydrogen  atoms  in  methane.  The 
interesting  question  suggests  itself  whether  the  hydrogen 
atoms  in  methane  all  bear  the  same  relation  to  the  carbon 
atom.  Assuming  that  the  carbon  atom  is  quadrivalent, 
and  that  each  of  the  four  hydrogen  atoms  is  in  combination 

H(l) 
I 
with  it,  as  indicated  in  the  formula  (4)  H-C-H  (2).     Do  the 

H(3) 
atoms  numbered  1,  2,  3,  and  4  bear  the  same  relation  to  the 


30  DERIVATIVES   OF   METHANE   AND   ETHANE 

carbon  or  not  ?  If  they  do  not,  then,  on  replacing  H  (1)  by 
chlorine,  the  product  should  be  different  from  that  obtained  by 
replacing  H  (2),  H  (3),  or  H  (4) ;  or,  it  should  be  possible 
to  make  more  than  one  variety  of  chlor-methane  and  of  similar 
products.  This  subject  is  an  extremely  difficult  one  to  deal 
with.  It  can  only  be  said  that,  although  chlor-methane  has 
been  made  in  several  ways,  the  product  obtained  is  always 
the  same  one;  and  the  same  is  true  of  all  other  substitution- 
products  of  methane.  So  far  as  evidence  of  this  kind  goes,  we 
have  no  reason  for  believing  that  there  are  any  differences  between 
the  hydrogen  atoms  of  methane. 

This  conclusion  is  of  fundamental  importance  in  dealing  with 
the  higher  members  of  the  methane  series,  and,  indeed,  in  deal- 
ing with  all  carbon  compounds,  as  will  be  seen  later. 

Chlor-ethane,  ethyl  chloride,  C2H5C1. 
Brom-ethane,  ethyl  bromide,  C2H5Br. 
lodo-ethane,  ethyl  iodide,  C2H5I. 

These  substances  are  all  liquids  having  pleasant  ethereal  odors. 
The  first  boils  at  12°,  the  second  at  38.8°,  and  the  third  at  7^2°. 
They  are  most  readily  made  from  alcohol,  by  treating  it  with 
the  corresponding  halogen  acids.  In  case  of  the  bromide  and 
iodide,  it  is  simpler  to  treat  the  alcohol  with  red  phosphorus 
and  the  halogen.  The  action  is  similar  to  that  involved  in 
making  hydrobromic  acid  by  treating  water  with  red  phosphorus 
and  bromine.  It  will  be  shown  that  alcohol  is  a  hydroxide 
in  which  hydroxyl  (OH)  is  in  combination  with  the  group  C2HS, 
called  ethyl,  as  represented  in  the  formula  C2H5.OH.  When 
bromine  is  brought  in  contact  with  red  phosphorus,  the  tribro- 
mide,  PBr3)  is  formed,  and  this  acts  upon  the  alcohol  thus :  — 

C2H5.OH       Brl 

C2HS.OH  +  Br  I  P  =  3  C2H5Br  +  P(OH)3. 

C2H5.OH       BrJ 

When  water  is  used  instead  of  alcohol,  the  bromine  appears  in 
combination  with  hydrogen  as  hydrobromic  acid. 


BROM-ETHANE 


31 


Experiment  6.  To  200s  (110cc)  concentrated  sulphuric  acid  in  a 
round  litre  flask  add  with  constant  shaking  without  cooling  90s  alcohol 
(about  95  per  cent).  After  cooling  to  the  temperature  of  the  room,  add 
carefully  75CC  ice- water,  with  continued  cooling,  and  then  100s  finely 


Fig.  5. 

pulverized  potassium  bromide.  Connect  the  flask  with  a  condenser  and 
heat  gently  as  long  as  anything  distils  over.  Place  the  distillate  in  a  glass- 
stoppered  cylinder,  and  shake  it  first  with  water  to  which  some  caustic 
soda  has  been  added,  and  then  two  or  three  times  with  water  alone. 
Separate  the  water  from  the  brom-ethane  by  means  of  a  separating  fun- 
nel. Add  two  or  three  pieces  of  fused  calcium  chloride  the  size  of  a  small 
marble,  and  let  stand  for  a  few  hours.  Then  pour  off  into  a  clean,  dry 
distilling  bulb,  and  distil,  noting  the  boiling  point. 

Among  the  many  halogen  substitution-products  of  ethane 
containing  more  than  one  halogen  atom,  only  two  will  be  men- 
tioned. These  are  the  two  di-chlor-ethanes,  both  of  which  are 
represented  by  the  formula  C2H4C12.  The  existence  of  these 
two  substances,  having  the  same  composition  but  entirely  dif- 
ferent properties,  affords  a  good  example  of  what  is  known  as 
isomerism. 


32  DERIVATIVES   OF   METHANE   AND   ETHANE 

Isomerism.  — One  of  the  most  striking  and  interesting  facts 
with  which  we  become  familiar  in  studying  carbon  compounds, 
is  the  frequent  occurrence  of  two,  and  often  more,  substances 
containing  the  same  elements  in  the  same  proportions  by  weight. 
Substances  which  bear  this  relation  to  one  another  are  said  to 
be  isomeric. 

Isomerism  is  of  two  kinds :  (1)  Substances  may  have  the  same 
percentage  composition  and  the  same  molecular  weights.  Such 
bodies  are  said  to  be  metameric.  The  di-chlor-ethanes,  C2H4C12, 
for  example,  are  metameric.  (2)  Substances  which  have  the 
same  percentage  composition  but  different  molecular  weights 
are  said  to  be  polymeric.  Acetylene,  C2H2,  benzene,  C6H6,  and 
styrene,  C8H8,  are  polymeric. 

The  cause  of  isomerism  is  undoubtedly  to  be  found  in  the 
different  relations  which  the  constituents  of  isomeric  com- 
pounds bear  to  each  other.  Our  structural  formulas,  which 
show  the  relations  between  the  parts  of  compounds  that 
have  been  traced  out  by  a  study  of  the  chemical  conduct  of 
these  compounds,  give  us  an  insight  into  the  causes  of  isomer- 
ism. To  illustrate,  let  us  take  the  two  di-chlor-ethanes.  One 
of  these  is  made  by  treating  ethane,  the  other  by  treating 
ethylene,  C2H4,  with  chlorine.  In  the  first  case  the  action  is 
substitution ;  in  the  second,  the  chlorine  is  added  directly  to 
ethylene,  thus,  — 

C2H4  +  01,  =  C2H4C12. 

The  product  from  ethylene  is  called  ethylene  chloride;  that 
from  ethane,  ethylidene  chloride.  It  will  be  shown  that  ethylene 

CH2 
is  to  be  represented  by  the  formula    |     ;   that  is,  that  in  it 

CH2 

only  two  hydrogen  atoms  are  in  combination  with  each  of  the 
carbon  atoms.  Now,  if  chlorine  is  brought  in  contact  with  this 
substance,  we  should  naturally  expect  each  of  the  carbon  atoms 
to  take  up  one  atom  of  chlorine,  and  thus  to  become  saturated, 
as  represented  in  the  equation,  — 


ISOMERISM  33 

CH2     Cl      CH2C1 
I      +      =  I 
CH2     Cl      CH2C1. 

Chlorine  is  taken  up,  and  it  is  believed  that  the  ethylene 
chloride  obtained  has  the  structure  represented  by  the  formula 
CH2C1 

I        ,  the  distinctive  feature  of  which  is  that  each  of  the 
CH2C1 
chlorine  atoms  is  in  combination  with  a  different  carbon  atom. 

We  can,  however,  conceive  of  another  possibility;  viz.,  both 
the  chlorine  atoms  may  be  in  combination  with  the  same 

CHC12 
carbon  atom,  as  represented  in  the  formula    |         ,   and  we 

CH3 

should  be  inclined  to  the  view  that  this  represents  the  structure 
of  ethylidene  chloride.  Fortunately  there  is  experimental  evi- 
dence to  support  this  view.  It  will  be  shown  that  aldehyde 

CHO 

has  the  formula  |       .     When  aldehyde  is  treated  with  phos- 

CH3 

phorus  pentachloride,  two  chlorine  atoms  take  the  place  of  the 
oxygen.  A  product  which  must  be  represented  by  the  formula 

CHC12 

I  is  formed,  and  this  is  identical  with  ethylidene  chloride. 
CH3 

Thus  it  will  be  seen  that  the  difference  between  the  two  iso- 
meric  compounds,  ethylene  chloride  and  ethylidene  chloride, 
depends  upon  the  fact  that  in  the  former  the  two  chlorine 
atoms  are  in  combination  with  different  carbon  atoms,  while 
in  the  latter  both  chlorine  atoms  are  in  combination  with  the 
same  carbon  atom. 

General  characteristics  of  the  halogen  derivatives  of  methane 
and  ethane.  The  one  characteristic  to  which  it  is  desirable 
that  special  attention  should  be  called  is  the  condition  of  the 
halogens  in  the  compounds.  In  general,  chlorine  in  combina- 
tion in  inorganic  compounds  can  be  detected  by  means  of  a 
solution  of  silver  nitrate,  for  when  dissolved  in  water  these 
compounds  are  ionized.  The  halogen  substitution  products  of 


34  DERIVATIVES    OF   METHANE   AND   ETHANE 

the  hydrocarbons  are  not  ionized  by  water,  and  the  chlorine 
in  them  cannot  be  detected  by  means  of  silver  nitrate  in  the 
ordinary  way.  On  the  other  hand,  when  chlor-methane  is 
heated  with  silver  nitrate  in  a  sealed  tube,  the  chlorine  is 
removed.  Sodium  and  zinc  have  the  power  of  extracting  the 
chlorine,  bromine,  etc.,  from  halogen  derivatives,  and  this  fact 
is  taken  advantage  of  in  the  synthesis  of  many  hydrocarbons. 
(See  "  Ethane,"  p.  25.) 


CHAPTER   IV 
OXYGEN  DERIVATIVES   OF  METHANE  AND  ETHANE 

THERE  are  several  classes  of  oxygen  derivatives  of  the  hydro- 
carbons. Among  them  are  the  important  compounds  known  as 
alcohols,  ethers,  aldehydes,  and  acids.  Each  of  these  classes 
will  be  taken  up  in  turn. 

1.    ALCOHOLS 

Among  the  most  important  oxygen  derivatives  are  the  alco- 
hols, of  which  methyl  'alcohol,  or  wood  spirit,  and  ethyl  alco- 
hol, or  spirit  of  wine,  are  the  best-known  examples.  As  far  as 
composition  is  concerned,  these  bodies  bear  very  simple  relations 
to  the  two  hydrocarbons,  methane  and  ethane.  These  relations 
are  indicated  by  the  formulas,  — 

Hydrocarbons  Alcohols 

CH4  CH40 

C2H6 


The  molecule  of  the  alcohol  differs  from  that  of  the  corre- 
sponding hydrocarbon  by  one  atom  of  oxygen.  In  order  to 
understand  the  chemical  nature  of  alcohols,  it  will  be  best  to 
study  with  some  care  the  reactions  of  one  ;  and  we  may  take 
for  this  purpose  the  simplest  one  of  the  series,  methyl  alcohol. 

Methyl  alcohol,  methanol,  CH4O.  —  This  alcohol  is  also 
known  as  wood  spirit.  It  is  found  in  nature  in  combination 
in  the  oil  of  winter  green.  It  is  formed,  together  with  many 
other  substances,  in  the  dry  distillation  of  wood.  It  is  hence 
contained  in  crude  pyroligneous  acid  or  wood  vinegar.  Wood 
is  distilled  in  large  quantities  for  various  purposes  j  chiefly, 

35 


36  DERIVATIVES   OF   METHANE   AND   ETHANE 

however,  for  making  charcoal.  In  most  charcoal  factories  the 
distillate  is  collected  and  utilized.  Wood  is  distilled  also  for 
the  purpose  of  making  pure  acetic  acid  and  its  salts. 

It  is  not  an  easy  matter  to  get  pure  methyl  alcohol  from 
crude  wood  spirit.  Fractional  distillation  alone  will  not  an- 
swer ;  though,  if  the  mixture  is  distilled  for  some  time,  and 
the  impure  alcohol  thus  obtained  then  converted  into  some 
crystalline  derivative,  the  latter  can  be  purified  and  then 
decomposed  in  such  a  way  as  to  yield  the  alcohol  in  pure 
condition. 

Methyl  alcohol  is  a  liquid  that  boils  at  66.7°,  and  has  the 
specific  gravity  0.8142  at  0°.  It  closely  resembles  ordinary 
alcohol  in  all  its  properties.  It  burns  with  a  non-luminous 
flame.  When  taken  into  the  system  it  intoxicates.  It  is 
poisonous.  Blindness  and  death  have  been  caused  by  its 
internal  use.  It  is  an  excellent  solvent  for  fats,  oils,  resins, 
etc.,  and  is  extensively  used  for  this  purpose. 

1.  Action   of  hydrochloric,  hydrobromic,  and  other  acids  on 
methyl  alcohol.     The  action  of  a  few  acids  is  represented  by 
the  following  equations: —        ^  , 

CH4Ot£  HBr  ^CH3Br  +  H20 ; 
CH40  +  HC1  =CH8C1  +H20; 
CH40  +  HN03  =  CHSN03  +  H20 ; 
CH40  +  H2S04  =  CH3.HS04  +  H20. 

The  action  is  plainly  suggestive  of  that  of  metallic  hydroxides 
or  bases.  In  each  case  the  acid  is  either  wholly  or  partly 
neutralized  and  water  is  formed,  just  as  the  acid  would  be 
neutralized  by  potassium  hydroxide. 

2.  Action  of  phosphorus  trichloride.     When  phosphorus  tri- 
chloride acts  on  methyl  alcohol,  the  products  are  chlor-methane 
and  phosphorous  acid  :  — 

3  CH40  -f  PC13  =  3  CH3C1  +  H3P03. 

Here  one  atom  of  chlorine  is  substituted  for  an  atom  of 
hydrogen  and  an  atom  of  oxygen,  the  reaction  being  like 


METHYL   ALCOHOL  37 

that  which  takes  place  between  water  and  phosphorus  tri- 
chloride :  — 

3  H20  +  PC13  =  3  HC1  +  H3P03 

This  fact  would  lead  us  to  suspect  that  there  is  some  resem- 
blance between  the  alcohol  and  water. 

3.  Action  of  potassium  and  sodium.  When  potassium  is 
brought  in  contact  with  pure  methyl  alcohol,  hydrogen  is  given 
off,  and  a  compound  containing  potassium  is  formed :  — 

CH40  +  K  =  CH3KO  +  H. 

Further  treatment  of  this  compound  with  potassium  causes  no 
further  evolution  of  hydrogen,  so  that  plainly  one  of  the  four 
hydrogen  atoms  contained  in  methyl  alcohol  differs  from  the 
other  three. 

The  resemblance  between  methyl  alcohol  and  metallic  hy- 
droxides ;  the  substitution  of  chlorine  for  hydrogen  and  oxygen ; 
and  the  resemblance  between  the  alcohol  and  water;  and,  finally, 
the  substitution  of  potassium  for  one,  and  only  one,  hydrogen 
atom,  lead  to  the  conclusion  that  the  alcohol  contains  hydrogen 
and  oxygen  in  combination,  and  that  the  characteristic  reac- 
tions are  due  to  the  presence  of  the  group  called  Jiydroxyl  (OH). 
The  analogy  between  the  alcohol,  a  metallic  hydroxide,  and 
water  is  shown  by  these  formulas :  alcohol,  CH3.OH  ;  hydroxide, 
K.OH ;  water,  H.OH.  Thus  water  appears  as  the  type  of  both 
the  hydroxide  and  the  alcohol,  and  they  may  be  regarded  as 
derived  from  water  by  substituting  the  group  CH3  for  one  hydro- 
gen atom  in  the  case  of  the  alcohol,  and  substituting  an  atom 
of  the  metal  potassium  for  one  hydrogen  atom  in  the  case 
of  the  hydroxide.  Or,  on  the  other  hand,  methyl  alcohol 
may  be  regarded  as  marsh  gas  in  which  one  of  the  hydrogen 
atoms  is  replaced  by  hydroxyl.  The  two  views  are  in  fact 
identical. 

To  test  the  correctness  of  the  view,  we  may  try  to  make 
methyl  alcohol  in  some  way  that  will  show  us  of  what  parts  it  is 
made  up.  Thus,  we  may  start  with  marsh  gas,  and  introduce  a 


38  DERIVATIVES    OF   METHANE   AND    ETHANE 

halogen,  as  bromine.  Now,  if  we  bring  brom-methane  together 
with  a  metallic  hydroxide,  the  bromine  and  the  metal  may 
unite,  leaving  the  hydroxyl  and  the  group  CH3,  which  may 
unite  also,  as  indicated  in  the  equation 

CH3Br  +  MOH  =  CH3.OH  +  MBr. 

If  methyl  alcohol  could  be  made  in  this  way,  we  should  have 
strong  evidence  in  favor  of  the  view  expressed  in  the  formula 
CH3.OH.  Methyl  alcohol  has  been  made  by  this  reaction;  and 
it  is  indeed  a  general  reaction  for  the  preparation  of  alcohols. 

The  reactions  above  presented  show  that  the  part  of  methyl 
alcohol  that  corresponds  to  the  metal  in  the  hydroxide  is  the 
group  CH3.  This  it  is  which  enters  into  the  acids  in  place  of 
their  hydrogen,  and  this  remains  unchanged  when  potassium 
acts  upon  the  alcohol.  It  has  received  the  name  methyl.  Hence 
we  have  the  names  methyl  alcohol,  methyl  bromide,  methyl 
ether,  etc.  A  group  which,  like  methyl,  appears  in  a  number 
of  compounds  is  called  a  radical,  or  residue.  These  names  are 
intended  simply  to  designate  that  part  of  a  carbon  compound 
which  remains  unchanged  when  the  compound  is  subjected  to 
various  transforming  influences. 

The  acid  formed  by  oxidation  has  the  composition  expressed 
by  the  formula  CH^.  It  contains  one  atom  of  oxygen  more 
and  two  atoms  of  hydrogen  less  than  the  alcohol  from  which  it  is 
formed.  It  will  be  shown  that  this  acid  is  the  first  of  an  import- 
ant series  of  acids,  known  as  the  fatty  acids,  each  of  which  bears 
the  same  relation  to  a  hydrocarbon  containing  the  same  number 
of  carbon  atoms  that  this  simplest  acid  bears  to  marsh  gas, 

The  two  most  characteristic  reactions  of  methyl  alcohol  are  : 
(1)  its  power  to  form  salt-like  compounds  when  treated  with 
acids  ;  and  (2)  its  power  to  form 


The  neutral  compounds  formed  with  acids  correspond  to  the 
salts  of  metals,  only  they  contain  the  radical,  or  residue,  methyl, 
CH3,  in  the  place  of  metals.  They  are  called  ethereal  salts,  or 
esters. 


FERMENTATION  39 

Ethyl  alcohol,  ethanol,  C2H5.OH.  —  This  is  the  best- 
known  substance  belonging  to  the  class  of  alcohols.  It  is 
known  also  by  the  name  spirit  of  wine  and  ordinary  alcohol. 
It  occurs  in  small  quantities  widely  distributed  in  nature. 

The  one  method  of  preparation  upon  which  we  are  dependent 
for  alcohol  is  the  fermentation  of  sugar. 

Fermentation.  —  Whenever  a  plant  juice  containing  sugar 
is  left  exposed  to  the  air,  it  gradually  undergoes  a  change  by 
which  it  loses  its  sweet  taste.  Usually  the  change  consists 
in  a  breaking  up  of  the  sugar  into  carbon  dioxide  and  alcohol. 
The  equation 

C6H1206  =  2  C2H60  +  2  C02, 

Sugar  Alcohol 

approximately  expresses  what  takes  place  in  the  process  which 
is  known  as  alcoholic  fermentation.  It  has  been  shown  that 
fermentation  is  caused  by  the  presence  of  small  organized 
bodies,  either  animal  or  vegetable.  These  bodies,  which  are 
known  as  ferments,  are  of  different  kinds,  and  cause  differ- 
ent kinds  of  fermentation  with  different  products.  Among 
the  kinds  of  fermentation  the  following  may  be  specially 
mentioned :  — 

1.  Alcoholic  or  vinous  fermentation.     This   is  caused   by  a 
vegetable  ferment  contained  in  ordinary  yeast.     The  ferment 
consists  of  small,  round  cells  arranged  in  chains.     The  prod- 
ucts  of  its  action  are  alcohol  and  carbon  dioxide. 

2.  Lactic  acid  fermentation.     This   is    due   to   a  vegetable 
ferment  which  is  contained  in  sour  milk.     It  has  the  power  of 
transforming  sugar  into  lactic  acid. 

3.  Acetic  acid  fermentation.     This  is  due  to  a  peculiar  vege- 
table ferment  which  acts  upon  alcohol,  transforming  it   into 
acetic  acid. 

The  germs  of  various  ferments_a^e__injthe_m^--aH4j- when- 
ever they  find  favorable  conditions^  they  develop  and  produce 
tHeir  cLaracteristic  effects.  They  will  not  develop  in  a  solution 


40  DERIVATIVES   OF   METHANE  AND   ETHANE 

of  pure  sugar.  The  variety  of  sugar  which  is  fermentable,  and 
which  is  the  one  from  which  alcohol  is  obtained,  is  not  our 
ordinary  cane  sugar,  but  one  known  as  grape  sugar,  or,  more 
commonly,  glucose.  In  order  that  the  ferments  may  grow,  there 
must  be  present  in  the  solution,  besides  the  sugar,  substances 
which  contain  nitrogen.  These,  as  well  as  the  sugar,  are  con- 
tained in  the  juices  pressed  out  from  fruits,  and  hence  these 
juices  readily  undergo  fermentation. 

In  the  manufacture  of  alcohol  a  solution  containing  sugar  is 
first  prepared  from  the  residue  of  wine  presses,  or  from  some 
kind  of  grain  or  potatoes.  In  case  the  solution  contains  grape 
sugar,  this  undergoes  fermentation  directly  when  the  yeast 
is  added.  If  the  substance  in  solution  is  cane  sugar,  this  is 
first  changed  by  the  enzyme,1  invertase,  present  in  the  yeast 
ferment  into  grape  sugar  and  fruit  sugar,  and  the  fermentation 
then  takes  place  as  in  the  first  case. 

Experiment  7.  Dissolve  about  150g  commercial  grape  sugar  in  1  to 
1|  litres  of  water  in  a  good-sized  flask.  Connect  the  flask  by  means  of 
a  bent  tube  with  a  cylinder  containing  clear  lime  water.  Protect  the 
latter  from  the  air  by  means  of  a  tube  containing  caustic  potash.  Now 
add  to  the  solution  of  grape  sugar  half  a  cake  of  compressed  yeast ;  close  the 
connections,  and  allow  to  stand.  Soon  an  evolution  of  gas  will  begin,  and, 
as  this  passes  through  the  lime  water,  a  precipitate  of  calcium  carbonate 
will  be  formed.  After  the  action  is  over,  place  the  flask  in  a  water-bath; 
connect  with  a  condenser,  and  distil  over  100CC  of  the  liquid.  Examine 
this  for  alcohol. 

A  good  way  to  detect  alcohol  is  this :  Warm  the  solution  to  be  tested  ; 
add  a  small  piece  of  iodine  and  then  caustic  potash  until  the  color  is 
destroyed.  On  cooling,  a  yellow  crystalline  substance,  iodoform,  is  de- 
posited if  alcohol  is  present. 

To  obtain  alcohol  from  fermented  liquids,  these  must  be  dis- 
tilled. The  ordinary  alcohol  contains  water,  and  a  mixture  of 

»  Enzymes,  substances  of  the  character  of  albumin,  have  the  power  to  bring  about  im- 
portant changes  in  some  of  the  carbohydrates.  They  are  called  unorganized  ferments,  as 
they  act  in  general  like  the  organized  ferments  or  ferments  proper.  Among  the  important 
enzymes  are  diastase  and  invertase. 


FERMENTATION  41 

other  alcohols  called  fusel  oil.  The  latter  can  be  removed  partly 
by  distillation,  and  the  last  portions  can  be  got  rid  of  by  fil- 
tering through  charcoal.  The  water  cannot  be  removed  com- 
pletely by  distillation,  though  a  product  containing  95.57  per 
cent  of  alcohol  can  be  obtained  in  this  way.  This  mixture, 
consisting  of  95.57  per  cent  alcohol  and  4.43  per  cent  water, 
has  a  constant  boiling-point  (78.15°). 

Absolute  alcohol  is  ordinary  alcohol  from  which  most  of  the 
water  has  been  removed  by  means  of  some  dehydrating  agent, 
as  quicklime  or  barium  oxide.  By  continued  treatment  with 
freshly  burned  lime  the  quantity  of  water  can  be  reduced  to 
one-half  a  per  cent,  and  this  small  quantity  can  be  removed  by 
treatment  with  metallic  sodium. 

Experiment  8.  Prepare  absolute  alcohol  from  ordinary  strong  alco- 
hol. For  this  purpose  a  good-sized  flask  is  one-half  to  two-thirds  filled 
with  quicklime  broken  into  small  lumps.  The  alcohol  is  poured  upon  the 
lime,  and  allowed  to  stand  at  least  twenty-four  hours,  when  it  is  distilled 
off  on  a  water-bath.  If  the  alcohol  used  contains  considerable  water,  it 
is  necessary  to  repeat  the  treatment  with  lime. 

Pure  ethyl  alcohol  has  a  peculiar,  pleasant  odor.  It  is 
claimed,  however,  that  perfectly  anhydrous  alcohol  has  no 
odor.  It  remains  liquid  at  very  low  temperatures,  but  it 
has  been  converted  into  a  solid  at  a  temperature  of  — 130.5°. 
It  boils  at  78.3°.  It  burns  with  a  non-luminous  flame,  which 
does  not  leave  a  deposit  of  soot  on  substances  placed  in  it.  It 
is  hence  used  for  heating  purposes.  When  mixed  with  air  its 
vapor  explodes  when  a  flame  is  applied.  Its  effects  upon  the 
human  system  are  well  known.  It  intoxicates  when  taken  in 
dilute  form,  while  in  concentrated  form  it  is  poisonous.  When 
taken  internally  in  large  doses,  it  lowers  the  temperature  of 
the  body  from  0.5°  to  2°,  although  the  sensation  of  warmth  is 
experienced. 

Alcohol  is  the  principal  solvent  for  substances  of  organic 
origin.  It  is  hence  extensively  used  in  the  arts,  as  in  the 
preparation  of  varnishes,  perfumes,  and  tinctures  of  drugs. 


42  DERIVATIVES   OF   METHANE    AND    ETHANE 

Denatured  alcohol.  —  Alcohol  to  which  something  has 
been  added  to  make  it  unfit  for  use  as  a  beverage  can  be  with- 
drawn from  bond  for  use  in  the  industries  without  payment  of 
the  internal  revenue  tax  on  alcohol.  Such  alcohol  is  called 
denatured  alcohol.  Various  substances  are  employed  as  dena- 
turing agents.  Those  authorized  by  the  United  States  govern- 
ment are  methyl  alcohol,  benzine,  and  pyridine  bases.  Ordinary 
denatured  alcohol  contains  methyl  alcohol  and  benzine.  Com- 
pletely denatured  alcohol  contains  methyl  alcohol  and  pyridine 
bases  (see  Pyridine  Bases,  page  350). 

Alcoholic  beverages.  —  Many  of  the  beverages  in  common 
use  depend  for  their  efficiency  upon  the  presence  of  alcohol  in 
greater  or  smaller  quantity.  The  milder  forms  of  beer  contain 
from  2  to  3  per  cent ;  light  wines,  such  as  claret,  about  8  per 
cent ;  while  whiskey,  brandy,  rum,  and  other  distilled  liquors 
sometimes  contain  as  much  as  60  to  75  per  cent.  These  dis- 
tilled liquors  are  ordinary  alcohol  with  water  and  small  quan- 
tities of  substances  obtaine'd  from  the  fruit  or  grain  used  in 
their  preparation,  or  obtained  by  standing  in  barrels  made 
of  oak  wood.  The  flavors  of  the  beverages  are  due  to  these 
substances. 

Chemical  conduct  of  ethyl  alcohol.  Ethyl  alcohol  conducts 
itself  chemically  like  methyl  alcohol.  The  products  formed 
contain  the  radical,  ethyl,  C2H5,  instead  of  methyl. 

2.   ETHERS 

When  an  alcohol  is  treated  with  potassium  or  sodium,  com- 
pounds are  formed  having  the  formulas,  CH3ONa,  CH3OK, 
C2H5OK,  C2H5ONa.  If  one  of  these  is  treated  with  a  mono- 
halogen  derivative  of  a  hydrocarbon,  as,  for  example,  iodo- 
methane,  CH3I,  reaction,  takes  place  thus :  — 

CH3ONa  +  CH3I  =  C2H60  +  Nal. 
This  reaction  leaves  very  little  room  for  doubt  in  regard  to 


ETHYL   ETHER  43 

the  structure  of  the  compound  C2H60.  It  must  be  represented 
by  the  formula  CH3-0-CH3,  or  (CH3)20.  Comparing 
it  with  methyl  alcohol,  it  will  be  seen  that  it  is  obtained 
from  the  alcohol  by  replacing  the  hydrogen  of  the  hydroxyl 
by  methyl,  CH3.  Just  as  the  alcohol  is  analogous  to  the  hy- 
droxide KOH,  so  the  new  compound  is  analogous  to  the  oxide, 
KoO.  It  is  the  representative  of  a  class  of  bodies  known  as 
ethers,  which  are  analogous  to  the  oxides  of  the  metals. 
Ordinary  ether  is  the  chief  representative  of  the  class. 

While  the  reaction  above  mentioned  serves  admirably  to 
show  the  relations  between  the  alcohols  and  ethers,  it  is  not 
the  one  that  is  made  use  of  in  their  preparation.  This  consists 
in  treating  the  alcohols  with  sulphuric  acid,  and  distilling. 

Ethyl  ether,  CiHioO  =  (C2H5)2O. — This  is  the  substance 
commonly  known  simply  as  ether,  or  sulphuric  ether.  The 
latter  name  was  originally  given  to  it  because  sulphuric  acid 
is  used  in  its  manufacture,  and  plainly  not  because  any 
sulphur  is  contained  in  it.  Ether  can  be  made  from  alcohol 
by  making  the  sodium  compound  of  alcohol,  C2H5ONa,  and 
heating  this  with  brom-  or  iodo-ethane  thus  :  — 

C2H5ONa  +  C2H5I  =  (C2H5)20  +  Nal ; 

or  by  converting  the  alcohol  into  ethyl  iodide  and  heating  this 
with  silver  oxide :  — 

2  C2H5I  +  Ag20  =  (C2H5)20  +  2  Agl. 

Ether  is  made  on  the  large  scale  by  mixing  sulphuric  acid 
and  alcohol  in  certain  proportions,  and  then  distilling  the 
mixture  with  more  alcohol  as  described  below.  Two  distinct 
reactions  are  involved  in  this  process.  First,  when  alcohol 
and  sulphuric  acid  are  brought  together,  half  the  hydrogen 
of  the  acid  is  replaced  by  ethyl,  thus :  — 

C2H5OH  +  ^  >  S04  =  °2^5  >  S04  +  H20. 
The  product  formed  is  called  ethyl-sulphuric  acid. 


44 


DERIVATIVES   OF   METHANE   AND   ETHANE 


Experiment  9.  Slowly  pour  20  to  30 cc  ordinary  concentrated  sul- 
phuric acid  into  about  the  same  volume  of  alcohol  of  80  to  90  per 
cent.  Stir  thoroughly,  and  dilute  with  a  litre  of  water.  In  an  evaporat- 
ing dish  add  powdered  barium  carbonate  until  the  liquid  is  neutral. 
Filter,  and  examine  the  clear  nitrate  for  barium.  Its  presence  shows 
that  a  soluble  barium  salt  has  been  formed.  This  is  barium  ethyl- 
sulphate,  Ba(C2H5S04)2. 

When  ethyl-sulphuric  acid  is  heated  with  alcohol,  ether  is 
formed,  and  sulphuric  acid  is  regenerated  thus :  — 

C2H5OH  +  °2^5  >  S04  =  °2J*  >  0  +  H2S04. 

The  ether  thus  formed  distils  over ;  and,  if  alcohol  is  admitted 
to  the  sulphuric  acid,  ethyl-sulphuric  acid  will  again  be 
formed,  and  with  excess  of  alcohol  it  will  yield  ether.  The 
actual  method  of  procedure  is  described  in 

Experiment  1O.  Arrange  an  apparatus  as  shown  in  Fig.  6.  As  ether 
is  very  volatile  and  inflammable,  it  is  important  that  the  condenser  be  con- 
nected with  the  receiver  as  shown,  and  the  receiver  placed  in  a  vessel  con- 


WlllluUHlH 

Fig.  6. 

taining  ice.  In  the  flask  put  a  mixture  of  200s  alcohol,  and  360s  ordinary 
concentrated  sulphuric  acid.  It  is  better  to  mix  them  in  another  vessel, 
and  allow  the  mixture  to  stand  for  some  time  until  it  is  thoroughly  cooled 


ETHYL   ETHER  45 

down;  and  then  to  pour  off  from  any  deposited  solid  as  completely  as 
possible.  Now  heat  until  the  thermometer  indicates  the  temperature  140°. 
At  this  point  the  mixture  boils,  and  ether  begins  to  pass  over.  As  soon 
as  this  is  noticed,  open  the  stop-cock  B,  and  let  a  slow  stream  of  alcohol 
pass  into  the  distilling  flask  through  the  tube,  which  must  reach  beneath 
the  surface  of  the  mixture.  Regulate  this  stream  so  that  the  tempera- 
ture remains  as  near  140°  as  possible.  After  about  250CC  of  alcohol  has 
been  admitted,  stop  the  operation.  Pour  the  distillate  into  a  glass-stop- 
pered cylinder,  and  add  water.  The  ether  will  rise  to  the  top, -forming  a 
layer,  and  can  be  removed  by  means  of  a  pipette  or  separating  funnel. 
It  should  be  shaken  in  this  way  a  few  times  with  water ;  then  treated 
with  a  little  fused  calcium  chloride  ;  and,  after  standing,  poured  off  into 
a  dry  flask,  and  distilled  on  a  water-bath. 

N.B.  Never  boil  ether  over  a  free  flame;  and,  in  working  with  it, 
always  carefully  avoid  the  neighborhood  of  flames.  In  boiling  it  on  a 
water-bath,  do  not  heat  the  water  to  boiling. 

Ether  is  a  colorless  liquid  of  peculiar  odor  and  taste.  It 
boils  at  34.9°.  Its  specific  gravity  is  0.736  at  0°.  It  is  very 
inflammable. 

Experiment  11.  Put  a  few  cubic  centimeters  of  ether  in  a  small 
evaporating  dish,  and  apply  a  flame. 

When  its  vapor  is  mixed  with,  air,  the  mixture  explodes 
violently  when  a  flame  is  applied.  Ether  is  somewhat  soluble 
in  water,  and  water  is  also  somewhat,  though  less,  soluble  in 
ether ;  so  that  when  the  two  are  shaken  together  the  volume 
of  the  ether  becomes  smaller,  even  though  every  precaution  is 
taken  to  avoid  evaporation.  Ether  mixes  with  alcohol  in  all 
proportions.  It  is  a  good  solvent  for  resins,  fats,  alkaloids, 
and  many  other  classes  of  carbon  compounds.  ;  • 

It  is  an  excellent  anaesthetic,  and  is  used  extensively  in  this 
capacity.  When  ether  is  brought  upon  the  skin  in  the  form  of 
spray,  the  cold  produced  by  the  rapid  evaporation  is  so  great 
as  to  cause  insensibility. 

Experiment  12.  In  a  thin  glass  test-tube  put  5CC  water.  Intro- 
duce the  tube  into  a  small  beaker  containing  some  ether.  Force  air 


46  DERIVATIVES   OF   METHANE    AND   ETHANE 

over  the  surface  of  the  ether  by  means  of  a  bellows.     The  water  will 
be  frozen. 

Chemical  conduct  of  ether.  As  we  have  seen,  its  synthesis 
from  sodium  ethylate,  C2H50]Sra,  and  iodo-ethane,  C2H5I,  leaves 
no  doubt  regarding  its  structure.  The  simplest  decompositions 
are  these  :  — 

Heated  with  acidified  water  to  150°  in  a  sealed  tube,  it  is 
converted  into  alcohol  :  — 

(C2H5)20  +  H20  =  2  C2H5OH. 

Treated  with  hydriodic  acid  at  a  low  temperature,  alcohol 
and  iodo-ethane  or  iodo-ethane  and  water  are  formed  :  — 

(C2H5)20  +  HI  =  C2H5OH  +  C2H5I. 
(C2H5)20  +  2  HI  =  2  C2H5I  +  H20. 

Mixed  ethers.  —  Just  as  ordinary  or  ethyl  alcohol  yields 
ethyl  ether,  so  methyl  alcohol  yields  methyl  ether,  (CH3)20. 
By  modifying  the  method,  a  mixed  ether)  methyl-ethyl  ether  , 


TT 

25 


>  0,  can  be  obtained.     This  is  formed  by  treating  sodium 

methylate  with  iodo-ethane,  or  by  treating  sodium  ethylate 
with  iodo-methane  :  — 

CH3ONa  +  C2H5I  =  ^  >0  +  Nal  ; 
bH3 

C2H6ONa  +  CH3I  L^5  >  0  +  Nal. 


It  is  formed  also  by  distilling  methyl  alcohol  with  ethyl-sul- 
phuric acid,  or  ethyl  alcohol  with  methyl-sulphuric  acid  :  — 

^•^3  ^  n   i  ^H5      Qn       C2H5       „ 
H  >  v  +      H  >  k(J4  =  ^,H  >  O  4- 

^2^5      ~      CH3  C2H5 

jj  >  U  +     jj  >  b(J4  =  ^,jj  >  U  + 

Methyl  ether  and  methyl-ethyl  ether  are  very  similar  to  ordi- 
nary ether. 


A 

KW\ 

\ 


<v  * 

ACETIC   ALDEHYDE  47 

3.   ALDEHYDES 


It  has  been  stated  above  that  when  methyl  and  ethyl  alcohols 
are  oxidized,  they  are  converted  into  acids  having  the  formulas 
CH202  and  C2H402,  respectively.  By  proper  precautions,  prod- 
ucts>  can  be  obtained  intermediate  between  the  alcohols  and 
acids,  and^  differing  from  them  in  composition  in  that  they 
contain  two  atomsjpf  hydrogen  less  than  the  corresponding 
alcohols.  These  products  are  called  aldehydes,  from  alcohoT 
^ehy^QpenaLum^To  in  the  fact  that  they  must  be  regarded  as 
"alconols  from  which  hydrogen  has  been  abstracted.  The  rela- 
tions in  composition  between  the  hydrocarbons,  alcohols,  and 
aldehydes  are  shown  by  these  formulas  :  — 

Hydrocarbons  Alcohols  Aldehydes 

CH4  CH40  CH20 

C2H6  C2H60  C2H40 

etc.  etc.  etc. 

Formic  aldehyde,  formal,  methanal,  CH2O.  —  This  alde- 
hyde is  made  by  passing  the  vapor  of  methyl  alcohol  together 
with  air  over  a  heated  platinum  or  copper  spiral.  When  cooled 
to  a  low  temperature  it  forms  a  liquid  that  boils  at  —  21°.  It 
is  manufactured  on  the  large  scale,  and  comes  into  the  market 
in  solution  under  the  name  of  formalin.  It  is  used  in  the  manu- 
facture of  some  dyes  and  as  a  preservative  and  disinfectant. 
When  its  solution  in  water  is  evaporated,  a  solid  substance 
having  the  same  composition  as  formic  aldehyde  is  obtained. 
This  is  a  polymeric  variety,  and  is  represented  by  the  formula 
(CH20)2.  It  is  called  paraformaldehyde. 

In  order  to  gain  a  clear  insight  into  the  nature  of  the  alde- 
hydes, it  will  be  best  to  study  the  best-known  representative  of 
the  class,  which  is  acetic  aldehyde. 


Acetic  aldehyde,    ethanal,    C2H4O.  —  This   aldehyde   is 
formed  whenever  alcohol  is  brought  in  contact  with  an  oxidizing 


48 


DERIVATIVES   OF  METHANE  AND   ETHANE 


mixture,  as,  for  example,  potassium   bichromate   and  dilute 
sulphuric  acid. 

Experiment  13.  Dissolve  a  little  potassium  bichromate  in  water, 
and  add  sulphuric  acid.  Now  add  a  few  cubic  centimetres  of  alcohol, 
and  notice  the  odor,  which  is  that  of  aldehyde.  Notice,  also,  the  change 
of  color  of  the  solution,  showing  the  reduction  of  the  bichromate. 

As  aldehyde  is  a  very  volatile  liquid,  it  is  difficult  to  collect  it. 
In  preparing  it,  it  is  therefore  best  to  pass  it  into  some  liquid 
which  will  absorb  it,  and  then  afterwards  separate  it  by  some 
appropriate  method.  A  good  method  is  that  described  below. 

Experiment  14.  Arrange  an  apparatus  as  shown  in  Fig.  7.  Put 
128s  granulated  potassium  bichromate  in  the  flask  A,  which  must 
have  a  capacity  of  1  to  2  litres.  Make  a  mixture  of  160s  con- 


Fig.  7.  P  48 

centrated  sulphuric  acid,  480s  water,  and  120s  alcohol.  Cool  the 
mixture  down  to  the  ordinary  temperature,  and  pour  it  into  the 
bottle  B.  Admit  this  mixture  slowly  to  the  flask.  The  cylinders 
C  and  D  are  about  half  filled  with  ordinary  ether,  each  one  con- 
taining about  200CC  ether,  and  placed  in  the  large  vessel  F,  which 


ACETIC  ALDEHYDE  49 

contains  ice  water.     The  condenser  should  be  supplied  with  water  of 
about  30°  C. 

Usually,  when  the  alcohol,  water,  and  sulphuric  acid  are  poured  upon 
the  bichromate,  the  action  begins  without  application  of  heat.  At  times 
it  takes  place  rapidly,  so  that  the  liquid  should  always  be  added  slowly. 
The  aldehyde  which  is  thus  formed,  together  with  some  alcohol  and 
water  vapor,  passes  into  the  condenser-tube,  where  the  greater  part  of 
the  alcohol  and  water  is  condensed  and  returned  to  the  flask,  while  the 
aldehyde,  being  much  more  volatile,  passes  into  the  ether  and  is  there 
absorbed.  After  the  action  is  over,  the  distilling  vessel  and  condenser 
are  removed,  and,  at  E,  connection  is  made  with  an  apparatus  furnishing 
dry  ammonia  gas.  The  gas  is  passed  into  the  cold  ethereal  solution  of 
aldehyde  to  the  point  of  saturation.  A  beautifully  crystallized  compound 
of  aldehyde  and  ammonia,  known  as  aldehyde-ammonia,  is  deposited.  The 
ether  is  poured  off,  and  the  crystals  placed  on  filter-paper^  They  gradually 
undergo  change  in  the  air,  becoming  yellow,  and  acquiring  a  peculiar 
odor.  If  the  crystals  are  placed  in  a  flask  and  treated  with  dilute  sulphuric 
acid,  pure  aldehyde  passes  over,  and  can  be  condensed  by  ice-cold  water. 

In  the  process  of  purification  of  ordinary  alcohol  it  is  filtered 
through  charcoal.  It  is  thus  partly  oxidized  to  aldehyde ;  and, 
when  it  is  afterwards  distilled,  the  first  portions  that  pass  over 
contain  aldehyde,  which  was  formerly  obtained  on  the  large 
scale  by  repeated  distillation  of  these  "  first  runnings." 

Aldehyde  is  a  colorless  liquid,  boiling  at  21°.  It  mixes  with 
water  and  alcohol  in  all  proportions.  Its  odor  is  marked  and 
characteristic. 

From  the  chemical  point  of  view,  the  most  characteristic 
property  of  aldehyde  is  its  power  to  unite  directly  with  other 
substances.  It  unites  with  oxygen  to  form  acetic  acid ;  with 
hydrogen  to  form  alcohol ;  with  ammonia  to  form  aldehyde- 
ammonia,  C2H4O.NH3;  with  hydrocyanic  acid  to  form  aldehyde 
hydrocyanide,  C2H4O.HCN ;  with  the  acid  sulphites  of  the 
alkalies  forming  compounds  represented  by  the  formulas 
C2H4O.HKS03  and  C2H4O.HNaS03 ;  and  with  other  substances. 
Indeed,  if  left  to  itself,  it  readily  changes  into  polymeric  modi- 
fications, uniting  with  itself  to  form  more  complex  compounds, 
paraldehyde  and  metaldehyde. 


50  DERIVATIVES   OF   METHANE  AND   ETHANE 

Par  aldehyde,  C6H12O3 —  This  is  formed  by  adding  a  few 
drops  of  concentrated  sulphuric  acid  to  aldehyde,  which  causes 
the  liquid  to  become  hot.  On  cooling  to  0°,  the  paraldehyde 
solidifies  in  crystalline  form.  It  melts  at  10.5°.  It  dissolves  in 
eight  times  its  own  volume  of  water,  and  boils  at  124°.  When 
distilled  with  dilute  sulphuric  acid,  hydrochloric  acid,  etc.,  it  is 
converted  into  aldehyde.  The  specific  gravity  of  its  vapor  has 
been  found  to  be  4.583.  This  leads  to  the  molecular  weight 
132.4,  and  consequently  to  the  formula  C6H1203.  It  is  called  a 
polymeric  modification  of  aldehyde.  It  is  used  in  medicine  as 
an  hypnotic. 

Metaldehyde,  G6H12O3 Metaldehyde  is  formed  in  much 

the  same  way  as  paraldehyde,  but  a  low  temperature  (below 
0°)  is  most  favorable  to  its  formation.  It  crystallizes  in 
needles,  which  are  insoluble  in  water,  and  but  slightly  soluble 
in  alcohol,  chloroform,  and  ether  in  the  cold,  though  more 
readily  at  a  slightly  elevated  temperature.  When  heated  to 
120°  in  a  sealed  tube,  it  is  converted  into  aldehyde.  Deter- 
minations by  the  freezing-point  method  show  that  the  molecu- 
lar weight  of  freshly  prepared  metal dehyde  is  the  same  as  that 
of  paraldehyde.  On  standing  it  is  converted  into  paraldehyde 
and,  probably,  a  substance  of  the  formula  (C2H40)4.  Distilled 
with  dilute  sulphuric  acid,  etc.,  metaldehyde  is  easily  con- 
verted into  aldehyde. 

In  consequence  of  the  tendency  of  aldehyde  to  unite  with 
oxygen,  it  is  a  strong  reducing  agent.  When  added  to  an  am- 
moniacal  solution  of  silver  nitrate,  metallic  silver  is  deposited 
on  the  walls  of  the  vessel  in  the  form  of  a  brilliant  mirror. 

Experiment  15.  To  a  dilute  solution  of  silver  nitrate  add  a  solution 
of  ammonia  until  the  silver  oxide  which  is  at  first  precipitated  is  nearly, 
though  not  quite,  dissolved  ;  filter,  warm  gently  in  a  clean  test-tube,  and 
add  a  few  drops  of  a  very  dilute  solution  of  aldehyde.  A  brilliant  mirror 
of  metallic  silver  will  appear.  This  method  is  used  in  the  manufacture 
of  mirrors.  What  becomes  of  the  aldehyde  ? 


ALDEHYDE  51 

Chemical  transformations  of  aldehyde.  As  aldehyde  is  pro- 
duced from  alcohol  by  oxidation,  so  alcohol  can  be  formed 
from  aldehyde  by  reduction  :  — 

C2H60  +  0   =  C2H40  +  H20; 
C2H40  +  H2=C2H60. 

By  oxidation  aldehyde  is  converted  into  an  acid  of  the  formula 
C2H402,  which  is  acetic  acid  ;  and,  by  reduction,  acetic  acid  is 
converted  into  aldehyde  :  — 

C2H40  +0  =  C2H402; 


Treated  with  phosphorus  pentachloride,  aldehyde  yields  ethyl- 
idene  chloride,  C2H4C12  (which  see).  This  reaction  is  of  special 
interest  and  importance,  as  it  helps  us  to  understand  the  relation 
between  aldehyde  and  alcohol.  Alcohol,  as  has  been  shown,  is 
the  hydroxide  of  ethyl,  C2H5.OH.  When  oxidized  it  loses  two 
atoms  of  hydrogen.  Is  the  hydrogen  of  the  hydroxyl  one  of 
the  two  which  are  given  off?  If  so,  what  readjustment  of  the 
oxygen  takes  place  ?  Such  are  the  questions  which  we  have  a 
right  to  ask. 

To  understand  the  action  of  phosphorus  pentachloride  on 
aldehyde,  it  will  be  necessary  to  consider  briefly  the  action  of 
this  reagent  in  general  upon  compounds  containing  oxygen. 
When  it  is  brought  in  contact  with  water,  the  first  change  is 
represented  by  the  equation 

H20-f-PCl5    =POC18  +  2HC1. 

Next,  the  oxichloride,  POC13,  is  acted  upon  thus  :  — 

3  H20  +  POCls  =  PO(OH)3  +  3  HC1. 

Or,  expressing  both  changes  in  one  equation,  we  have  :  — 

4  H20  +  PC15    =  PO  (OH).  +  5  HC1. 

The  phosphorus  pentachloride  gives  up  its  chlorine  and  takes 
up  oxygen,  or  oxygen  and  hydrogen,  in  its  place.  This  is  the 
general  tendency  of  the  chlorides  of  phosphorus. 


52  DERIVATIVES   OF  METHANE   AND   ETHANE 

Now,  when  a  chloride  of  phosphorus  is  brought  together 
with  an  alcohol,  chlorine  is  substituted  for  the  oxygen,  two 
atoms  of  the  former  for  one  of  the  latter,  thus  :  — 

C2H5.OH  +  PC15  =  C2H5C1.C1H  +  POOL, 

But  as  hydroxyl,  —  0  —  H,  is  univalent,  its  place  cannot  be 
taken  by  two  atoms  of  chlorine  and  one  of  hydrogen,  and  the 
two  chlorine  atoms  have  not  the  power  of  linking  the  hydrogen 
to  the  ethyl.  Hydrochloric  acid  is  given  off,  and  a  compound  is 
formed,  which  may  be  regarded  as  alcohol  in  which  one  chlorine 
atom  takes  the  place  of  the  hydroxyl.  This  is  the  kind  of 
action  that  takes  place  whenever  a  chloride  of  phosphorus  acts 
upon  a  compound  containing  hydroxyl  ;  and  hence  the  reaction 
is  made  use  of  for  determining  whether  hydroxyl  is  or  is  not  pres- 
ent in  a  compound. 

When  aldehyde  is  treated  with  phosphorus  pentachloride, 
the  action  is  entirely  different  from  that  just  described.  Instead 
of  one  chlorine  atom  taking  the  place  of  a  hydrogen  and  an 
oxygen  atom,  two  chlorine  atoms  take  the  place  of  the  oxygen 
atom  :  - 


If  the  explanation  above  offered  of  the  action  of  phosphorus 
pentachloride  on  alcohol  is  correct,  it  follows  that  aldehyde  is 
not  a  hydroxyl  compound.  We  can  readily  understand  why  two 
chlorine  atoms  should  take  the  place  of  the  oxygen  atom,  if  the 
latter  is  in  combination  only  with  carbon  as  in  carbon  monoxide, 
CO.  There  is  an  essential  difference  between  this  kind  of  com- 
bination and  that  which  we  have  in  hydroxyl  as  C  —  0  —  H.  la 
the  latter  condition  the  oxygen  serves  to  connect  carbon  with 
hydrogen;  in  the  former  it  is  in  combination  only  with  the 
carbon,  and,  presumably,  the  force  which  holds  it  can  also  hold 
two  atoms  of  chlorine  or  of  any  other  univalent  element  with 
which  it  can  unite.  So  that,  if  oxygen  is  in  a  compound  in  the 
carbon  monoxide  condition,  we  should  expect  two  chlorine 
atoms  to  take  its  place  when  the  compound  is  treated  with 


ALDEHYDE  53 

phosphorus  pentachloride.  Let  R.CO  represent  any  such  com- 
pound ;  then  we  should  have :  — 

ECO  +  PC15  =  R.CC1,  +  POC13; 

while,  when  oxygen  is  present  in  the  hydroxyl  condition,  we 
have : — 

R.C  -  0  -  H  +  PC15  =  R.CC1  +  POC13  + HC1. 

Just  as  the  latter  reaction  is  used  to  detect  the  presence  of 
hydroxyl  oxygen,  so  the  former  is  used  to  detect  oxygen  in  the 
other  condition,  which  is  commonly  known  as  the  carbonyl 
condition. 

In  terms  of  the  valence  hypothesis,  it  is  said  that  in  the 
hydroxyl  compounds  oxygen  is  in  combination  with  carbon  with 
one  of  its  affinities,  and  with  hydrogen  with  the  other,  while  in 
the  carbonyl  compounds  it  is  in  combination  with  carbon  with 
both  its  affinities  as  represented  thus,  C  =  0. 

According  to  the  above  reasoning  aldehyde  is  a  carbonyl 
compound,  or  it  contains  the  group  CO.  The  simplest  alde- 
hyde must  therefore  be  represented  by  the  formula  H2C  =  0. 

O 
II 

Its  homologue,  acetic  aldehyde,  is  CH3.C— H.    The  peculiar  prop- 
erties of  aldehyde  are  believed  to  be  due  to  the  presence  of  this 
O 
II 

group,  C  —  H,  which  is  called  the  aldehyde  group.  We  do 
not  know  that  the  double  line  in  the  formula  conveys  a 
correct  idea  in  regard  to  the  relation  between  the  carbon 
and  oxygen.  All  that  we  know  is  that  these  two  elements 
do  occur  in  two  different  relations  to  each  other,  and  the 
formulas  C  — 0  — H  and  C  =  0  recall  these  relations.  They 
are  expressions  of  facts  established  by  experiment.  Our 
notions  in  regard  to  these  relations  are  largely  dependent 
upon  the  reactions  with  the  chlorides  of  phosphorus  referred 
to  above. 


54  DERIVATIVES   OF   METHANE   AND   ETHANE 

Chloral,  trichlor aldehyde,  CC13CHO.  —  When  chlorine 
acts  directly  upon  aldehyde,  complicated  reactions  take  place 
which  need  not  be  discussed  here.  If,  however,  water  and 
calcium  carbonate  are  present,  substitution  takes  place,  and 
trichlor  aldehyde  is  formed.  When  alcohol  is  treated  with 
chlorine,  a  double  action  takes  place:  The  alcohol  is  first 
changed  to  aldehyde  thus:  — 

CH3.CH2OH  +  C12  =  CH3.COH  +  2  HC1. 

Then  the  chlorine  acts  upon  the  aldehyde,  and  is  substituted 
for  the  three  hydrogens  of  the  methyl,  forming  trichloralde- 

hy de : — 

CH3.COH  +  6  Cl  =  CC13.COH  +  3  HC1. 

In  reality  the  aldehyde  first  formed  acts  upon  the  alcohol, 
forming  an  intermediate  product  which  is  acted  upon  by  the 
chlorine ;  and  the  chlorine  product  thus  formed  breaks  up,  form- 
ing chloral.  The  essential  features  of  the  reaction,  however, 
are  stated  in  the  above  equations.  Trichloraldehyde  is  the 
substance  commonly  known  as  chloral.  It  is  simply  the  tri- 
chlorine  substitution  product  of  aldehyde.  It  has  all  the  gen- 
eral properties  of  aldehyde,  and  the  conclusion  is  therefore 

O 
II 
justified  that  it  contains  the  aldehyde  group  -  CH. 

Chloral  is  a  colorless  liquid,  which  boils  at  98°,  and  has  the 
specific  gravity  1.54  at  0°. 

NOTE  FOR  STUDENT.  —  Give  the  formulas  of  compounds  formed  when 
chloral  is  brought  together  with  ammonia,  hydrocyanic  acid,  and  the  acid 
sulphites  of  the  alkalies.  What  is  the  formula  of  the  acid  formed  by  its 
oxidation  ?  The  answer  is  given  in  the  statement  that  the  general  chemi- 
cal conduct  of  chloral  is  the  same  as  that  of  aldehyde. 

When  chloral  and  water  are  brought  together,  they  unite  to 
form  a  crystallized  compound,  chloral  hydrate,  C2HC130  -}-  H20, 
which  is  easily  soluble  in  water,  and  crystallizes  from  the  solu- 
tion in  beautiful,  colorless,  monoclinic  prisms.  It  melts  at  57° 


FORMIC    ACID  55 

and  boils  at  97.5°,  dissociating  into  chloral  and  water.  Taken 
internally  in  doses  of  from  0.6  to  2g,  it  produces  sleep.  In 
larger  doses  it  acts  as  an  anaesthetic. 

When  treated  with  an  alkali,  chloral  and  chloral  hydrate 
break  up,  yielding  chloroform  and  formic  acid :  — 

CC13.COH  +  KOH  =  CHC13  +  KCH02. 

Chloral  Chloroform  Potassium 

formate 

Similar  reactions  take  place  in  the  preparation  of  chloroform 
and  iodoform  from  alcohol. 

NOTE  FOR  STUDENT.  — How  is  chloroform  made  ?  How  is  the  method 
explained?  Answer  the  same  questions  for  iodoform.  The  bleaching 
powder  used  in  preparing  chloroform  furnishes  chlorine.  Is  an  alkali 
present  ? 

4.   ACIDS 

When  methyl  and  ethyl  alcohols  are  oxidized,  they  are  con- 
verted  first  into  aldehydes,  and  then  the  aldehydes  take  up 
oxygen  and  are  converted  into  acids.  The  relations  in  compo- 
sition between  the  hydrocarbons,  alcohols,  aldehydes,  and  acids 
are  shown  in  the  subjoined  table  :*—  ^  ]  j 

Hydrocarbons  Alcohols  'Aldehydes  Acids 

CH4  CH40  ,CH20  CH202 

C2H6  C2H60  ^J)tf2H40  C2H408 

etc.  etc.          -      etc.  etc. 

The  two  acids  whose  formulas  are  here  given  are  the  well- 
known  substances,  formic  and  acetic  acids. 

f")     ""    C    '     rf\  I 

Formic  acid,  methanic  acid,  CH2O2.  —  This  acid  occurs 
in  nature  in  red  ants,  in  stinging  nettles,  in  the  shoots  of  some 
of  the  varieties  of  pine,  and  elsewhere. 

It  can  be  obtained  by  distilling  red  ants,  and  is  best  pre- 
pared by  heating  oxalic  acid  with  glycerol.  Oxalic  acid  has  the 
composition  represented  by  the  formula  C2H204.  When  heated 


56  DERIVATIVES   OF  METHANE   AND   ETHANE 

in  glycerol  to  100°-110°  it  breaks  down  into  carbon  dioxide  and 

formic  acids-       c2HA  =  C02  +  CH20, 

The  formic  acid  distils  over,  and  can  be  condensed. 

Experiment  16.  Into  a  flask  of  500  to  600CC  capacity  put  200  to 
300CC  anhydrous  glycerol,  and  then  add  30  to  40s  crystallized  oxalic 
acid.  Connect  the  flask  with  a  condenser,  and  insert  a  thermometer 
through  the  cork  so  that  the  bulb  is  below  the  surface  of  the  glycerol. 
Heat  gently.  At  75°  to  90°,  carbon  dioxide  is  evolved.  Raise  the  tem- 
perature gradually  to  125°-130°.  When  formic  acid  no  longer  distils 
over,  add  another  portion  of  oxalic  acid,  and  heat  again.  This  opera- 
tion may  be  repeated  a  number  of  times  without  renewing  the  glycerol  ; 
but,  when  about  100s  of  oxalic  acid  has  been  decomposed,  enough 
formic  acid  for  the  purpose  will  have  been  formed,  and  collected  in 
the  receiver.  Dilute  the  distillate  to  about  half  a  litre,  and,  while 
gently  warming  it  in  an  evaporating  dish,  add  freshly  precipitated  and 
washed  copper  oxide  in  small  quantities  until  no  more  is  dissolved. 
Then  filter,  and  evaporate  the  solution  to  crystallization.  The  beauti- 
fully crystallized  salt  thus  obtained  is  copper  formate. 

The  formation  of  formic  acid  by  oxidation  of  methyl  alcohol, 
and  by  treatment  of  chloral  with  an  alkali,  has  already  been 
mentioned.  The  following  methods  are  of  special  interest:  — 

(1)  By  the  action  of  carbon  monoxide  upon  sodium  hy- 
droxide:- C() 


This  method  is  nsed  for  the  preparation  of  formic  acid  on  the 
large  scale,  soda-lime  being  used  instead  of  sodium  hydroxide. 

(2)  By  the  action  of  metallic  potassium  upon  moist  carbon 
dioxide  (carbonic  acid)  :  — 

2  C02  +  2  K  +  H20  =  HC02K  +  HC03K, 
or  2  C03H2  +  2  K  =  HC02K  +  HC03K  +  H20. 

(3)  By  treatment  of  a  solution  of  ammonium  carbonate  with 
sodium  amalgam  :  — 

C03(NH4)2  +  2  H  =  HC02(NH4)  +  H20  +  NH3, 
and      HC02(NH4)  +  NaOH  =  HC02Na  +  NH3  +  H2O. 


FORMIC   ACID  57 

According  to  these  last  two  methods  formic  acid  appears  as  a 
reduction  product  of  carbonic  acid  formed  by  the  abstraction 
of  one  atom  of  oxygen  :  — 


It  will  be  shown  that  all  the  acids  of  carbon  may  be  regarded 
as  derivatives  of  either  formic  acid  or  carbonic  acid. 

(4)  When  hydrocyanic  acid  is  -treated  with  an  acid  or  an 
alkali,  it  gives  ammonia  and  formic  acid.  The  reaction  may 
be  represented  thus  :  — 

HCN  +  2  H20  =  H2C02  +  NH3. 

Of  course,  if  an  acid  is  present,  the  ammonium  salt  of  the  acid 
is  formed  ;  and,  if  an  alkali  is  present,  the  formate  of  this  alkali 
is  formed.  A  reaction  similar  to  this  is  used  very  extensively  in 
the  preparation  of  the  acids  of  carbon,  as  will  be  shown. 

Anhydrous  formic  acid  can  be  made  by  dehydrating  either 
the  copper  or  lead  salt,  and  passing  dry  hydrogen  sulphide 
over  the  salt  placed  in  a  heated  tube,  or  by  heating  a  mixture 
of  dry  sodium  formate  and  acid  sodium  sulphate  :  — 

HC02Na  +  NaHS04  =  Na2S04  +  H2C02. 

It  is  a  colorless  liquid  boiling  at  99°  at  760mm.  It  has 
a  penetrating  odor.  Dropped  on  the  skin,  it  causes  extreme 
pain  and  produces  blisters.  Its  specific  gravity  at  0°  is  1.22. 
When  cooled  down  it  solidifies  to  a  mass  of  crystals  which  melt 
at  8.6°.  It  is  a  stronger  acid  than  acetic  acid.  It  is  a  power- 
ful antiseptic. 

Concentrated  sulphuric  acid  decomposes  it  into  carbon  mon- 
oxide and  water  :  — 

H2C02  =  CO  +  H20. 

It  is  easily  oxidized  to  carbonic  acid.  Hence  it  acts  as  a 
reducing  agent.  Heated  with  the  oxides  of  mercury  or  silver, 
they  are  reduced  to  the  metallic  condition  :  — 

HgO  +  H2C02  =  Hg  +  H20  +  C02. 
Like  other  acids,  formic  acid  yields  a  large  number  of  salts  with 


58  DERIVATIVES   OF  METHANE    AND   ETHANE 

bases,  and  ethereal  salts  or  compound  ethers  with  the  alcohols. 
These  derivatives  need  not  be  treated  of  here.  The  salts  are 
all  soluble  in  water,  and  some  of  them,  as  the  lead,  copper,  and 
barium  salts,  crystallize  very  well.  Some  of  the  ethereal  salts 
will  be  mentioned  when  these  substances  are  taken  up  as  a  class. 

Acetic  acid,  ethanic  acid,  C2H4O2.  —  Acetic  acid  is  made 

(1)  By  the  oxidation  of  alcohol ;  and 

(2)  By  the  distillation  of  wood. 

When  pure  alcohol  is  exposed  to  the  air  it  undergoes  no 
change;  If,  however,  some  platinum  black  is  placed  in  it, 
oxidation  takes  place  and  acetic  acid  is  formed.  So  also  if 
fermented  liquors  that  contain  nitrogenous  substances  are 
exposed  to  the  air,  oxidation  takes  place,  and  the  liquor  be- 
comes sour  in  consequence  of  the  formation  of  acetic  acid.  A 
great  deal  of  acetic  acid  is  made  by  exposing  poor  wine  to  the 
action  of  the  air.  The  product  is  known  as  wine  vinegar. 
The  formation  of  vinegar  has  been  shown  to  be  due  to  the 
presence  of  a  microscopic  organism  (Mycoderma  aceti)  com- 
monly known  as  "  mother-of- vinegar."  This  serves  in  some 
way  to  convey  the  oxygen  from  the  air  to  the  alcohol.  The 
"  quick-vinegar  process,"  much  used  in  the  manufacture  of 
vinegar,  consists  in  allowing  weak  spirits  of  wine  to  pass 
slowly  through  barrels  filled  with  beech  shavings  which  have 
become  covered  with  Mycoderma  aceti.  The  presence  of  the 
organism  is  secured  by  first  pouring  strong  vinegar  into  the 
barrels,  and  allowing  it  to  stand  for  one  or  two  days  in  con- 
tact with  the  shavings. 

When  wood  is  distilled,  a  very  complex  mixture  passes  over, 
one  of  the  constituents  being  acetic  acid.  By  keeping  the 
temperature  down  comparatively  low,  the  amount  of  acetic 
acid  obtained  is  increased.  The  distillate  is  neutralized  with 
soda  ash,  and  the  solution  of  crude  sodium  acetate  thus  ob- 
tained evaporated  to  dryness.  It  is  then  treated  with  sul- 
phuric acid,  and  distilled,  when  acetic  acid  passes  over. 


ACETIC   ACID  59 

There  are  three  other  methods  which  may  be  used  for  making 
acetic  acid.  They  are, — 

(1)  By  treating  sodium  methylate  with  carbon  monoxide :  — . 

CH3ONa  +  CO  =  CH3.C02Na. 

(2)  By  treating  carbon  dioxide  with  sodium-methyl :  — 

C02  +  CH3STa  =  CH3.C02Na. 

(3)  By  treating  methyl  cyanide,  CH3CN,  with  an  acid  or  an 

pi  IT- O  1  1    •    ,. 

CH3CN  +  2  H20  =  CH3.C02H  +  NH3. 

This  reaction  is  analogous  to  that  involved  in  the  formation 
of  formic  acid  from  hydrocyanic  acid  (see  p.  57). 

To  purify  the  acid  it  is  passed  through  charcoal  and  dis- 
tilled. It  still  contains  water,  from  which  it  cannot  be  com- 
pletely separated  by  distillation.  When  cooled  to  a  low 
temperature  it  solidifies,  and  the  water  can  then  partly  be 
poured  off.  By  repeating  the  freezing,  and  distilling  a  few 
times,  pure,  anhydrous  acetic  acid  can  be  obtained. 

Experiment  17.  Make  pure  acetic  acid  from  the  commercial  sub- 
stance. First  distil  in  fractions  until  a  portion  is  obtained  that  boils 
between  110°  and  119°.  Put  the  vessel  containing  this  in  ice.  The 
liquid  will  solidify  almost  completely.  Pour  off  the  little  liquid  which 
remains,  and  distil. 

Acetic  acid  is  a  clear,  colorless  liquid,  which  boils  at  118°. 
It  has  a  very  penetrating,  pleasant,  acid  odor,  and  a  sharp  acid 
taste.  The  pure  substance  acts  upon  the  skin  like  formic  acid, 
causing  pain  and  raising  blisters.  It  solidifies  when  cooled  down, 
and  the  crystals  melt  at  16.7°.  The  pure  acid  which  is  solid  at 
temperatures  below  16°  is  known  as  glacial  acetic  acid.  Its  spe- 
cific gravity  is  1.08  at  0°.  It  mixes  with  water  in  all  proportions. 

Acetic  acid  is  extensively  used,  chiefly  in  the  dilute,  impure 
form  known  as  vinegar,  which  is  an  aqueous  solution  of  acetic 
acid  containing  from  3  to  6  per  cent  of  the  acid,  a  little  alcohol, 
and  other  substances  in  small  quantities.  It  is  used  in  calico 
printing  in  the  form  of  iron  and  aluminium  salts.  With  iron  it 


60  DERIVATIVES   OF   METHANE   AND   ETHANE 

gives  hydrogen,  which  is  needed  in  the  manufacture  of  certain 
compounds  used  in  making  dyes,  as,  for  example,  aniline. 
Glacial  acetic  acid  is  an  excellent  solvent  for  many  organic  sub- 
stances, and  is  therefore  frequently  used  in  scientific  researches. 

Derivatives  of  acetic  acid.  Acetic  acid  yields  a  large  num- 
ber of  derivatives.  They  may  be  treated  of  briefly  under  two 
heads:  (1)  Those  which  are  formed  in  consequence  of  the 
acid  properties  and  which  necessitate  a  loss  of  the  acid  proper- 
ties, as  the  salts,  ethereal  salts,  etc. ;  and  (2)  those  in  which 
the  acid  properties  remain  essentially  unchanged. 

Salts  of  acetic  acid.  The  acetates  of  the  alkalies  were  the 
first  compounds  of  carbon  ever  prepared.  The  potassium  and 
sodium  salts  are  used  in  the  chemical  laboratory.  Both  crystal- 
lize, the  sodium  salt  particularly  well  and  easily. 

Lead  acetate,  (C2H302)2Pb  -f-  3  H20.  This  salt,  which  is  com- 
monly  known  as  sugar  of  lead,  is  made  on  the  large  scale  by 
dissolving  lead  oxide  in  acetic  acid.  It  crystallizes  well,  and 
is  soluble  in  1.5  parts  of  water  at  ordinary  temperatures.  Com- 
mercial sugar  of  lead  frequently  contains  an  excess  of  lead 
oxide  in  the  form  of  basic  salts.  A  solution  of  such  a  mixture 
becomes  turbid  when  allowed  to  stand  in  the  air,  or  gives  a 
precipitate  when  dissolved  in  ordinary  spring  water,  in  conse- 
quence of  the  formation  of  lead  carbonate. 

Copper  acetate,  (C2H302)2Cu  +  2  H20.  This  salt  can  be  made 
by  dissolving  copper  hydroxide  or  carbonate  in  acetic  acid.  It 
crystallizes  in  dark-blue,  transparent  prisms.  A  basic  acetate, 
formed  by  the  action  of  acetic  acid  on  copper  in  the  air,  is 
known  as  verdigris. 

Copper  aceto-arsenite,  3  CuAs204  +  (C2H302)2Cu.  This  double 
salt  is  formed  by  boiling  verdigris  and  arsenic  trioxide  together 
in  water.  It  has  a  fine  bright-green  color,  and  is  used  as  a 
pigment  and  as  an  insecticide.  It  is  the  chief  constituent  of 
emerald  green,  Paris  green,  or  Schweinfurt's  green. 

Iron  forms  two  distinct  salts  with  acetic  acid,  the  ferrous 
salt,  (C2H302)2Fe  +  4  H20,  and  the  ferric  salt,  (C2H302)3Fe. 


ACETIC   ANHYDRIDE  61 

The  latter  is  formed  when  sodium  acetate  is  added  to  an  acidi- 
fied solution  of  a  ferric  salt.  At  first  the  solution  becomes 
deep-red  in  color ;  but,  on  boiling,  all  the  iron  is  precipitated 
as  hydroxide.  Hence  this  salt  is  used  for  the  purpose  of  sepa- 
rating iron  from  manganese  in  analytical  operations. 

Experiment  18.  To  a  dilute  solution  of  ferric  chloride,  contained 
in  a  small  flask,  add  a  little  acetic  acid  and  a  solution  of  sodium  acetate. 
Boil  the  red  solution,  and  ferric  hydroxide  is  precipitated,  leaving  the 
solution  colorless.  Filter,  and  examine  the  filtrate  for  iron. 

The  ethereal  salts  will  be  mentioned  briefly  when  this  class 
of  compounds  is  taken  up.  The  principal  one  is  ethyl  acetate 
or  acetic  ether,  which  is  formed  from  acetic  acid  and  ordinary 
alcohol.  When  a  mixture  of  these  two  substances  is  treated 
with  sulphuric  acid,  the  ether  is  formed  and  can  be  recognized 
by  its  pleasant  odor.  This  fact  is  taken  advantage  of  for  the 
detection  of  acetic  acid. 

Experiment  19.  To  a  mixture  of  about  equal  parts  of  acetic  acid 
and  alcohol,  in  a  test-tube,  add  a  little  concentrated  sulphuric  acid,  heat, 
and  notice  the  odor.  It  is  that  of  ethyl  acetate  or  acetic  ether. 


Acetyl  chloride,  C2H3OC1. 
Acetyl  bromide,  C2H3OBr. 
Acetyl  iodide,  C2H3OI. 


Just  as  alcohol,  when 
treated  with  phosphorus  tri- 
chloride, yields  a  chloride  of 


ethyl,  so  acetic  acid,  when  treated  with  the  same  reagent,  yields 
acetyl  chloride.  The  character  of  the  reaction  is  the  same  in 
both  cases.  It  consists  in  the  substitution  of  chlorine  for 
hydroxyl :  — 

3  CH3.COOH  +  PC13  =  3  CH3.COC1  +  H3P03. 

Acetyl  chloride 

Experiment  20.  Arrange  a  dry  distilling  flask,  with  condenser  and 
dry  receiver,  under  a  hood  or  out  of  doors.  Bring  together  9  parts 
(say  180s)  strong  acetic  acid  and  6  parts  (say  120?)  phosphorus  tri- 
chloride. Heat  the  mixture  gently  on  the  water-bath,  when  acetyl 
chloride  will  distil  over.  Collect  in  a  dry  bottle. 

Acetyl  chloride  is  a  colorless   liquid  which  boils  at  51°. 


62  DERIVATIVES   OF   METHANE   AND   ETHANE 

Water  acts  upon  it  very  readily,  acetic  and  hydrochloric  acids 
being  formed :  — 

C2H3OC1  +  H20  =  C2H3O.OH  +  HC1. 

In  this  case  the  chlorine  is  replaced  by  hydroxyl.  As  the 
substance  is  volatile,  it  fumes  in  contact  with  the  air  in  conse- 
quence of  the  formation  of  hydrochloric  acid.  It  must  be 
kept  in  tightly-stoppered  bottles.  In  handling  it,  care  must 
be  taken  not  to  bring  it  near  the  nose,  as  the  vapor  is  suf- 
focating, and  it  attacks  the  mucous  membranes  of  the  eyes  and 
nose,  producing  coughing  and  other  bad  results. 

Acetyl  chloride  is  a  valuable  reagent  much  used  in  the  ex- 
amination of  compounds  of  carbon.  Its  value  depends  upon 
its  action  towards  alcohols.  When  it  is  brought  together  with 
an  alcohol,  as,  for  example,  methyl  alcohol,  hydrochloric  acid 
is  evolved,  and  the  acetyl  group  takes  the  place  of  the  hydro- 
gen of  the  alcoholic  hydroxyl :  — 

CH3.OH  +  C2H3OC1  =  CH3.O.C2H30  +  HC1. 

The  product  is  an  ethereal  salt,  methyl  acetate.  This  kind  of 
action  takes  place  whenever  an  alcohol  is  treated  with  acetyl 
chloride.  Hence  if,  on  treating  a  substance  with  acetyl  chlo- 
ride, its  composition  is  changed,  showing  that  hydrogen  is 
replaced  by  acetyl,  we  are  justified  in  concluding  that  the  sub- 
stance contains  alcoholic  hydroxyl.  The  bromide  and  iodide 
resemble  the  chloride  very  closely. 

Experiment  21.  Treat  a  few  cubic  centimetres  of  absolute  alcohol 
with  acetyl  chloride.  Notice  the  evolution  of  hydrochloric  acid  and  the 
odor  of  ethyl  acetate. 

Acetic  anhydride  or  acetyl  oxide,  C4H6O3.  This  is  made 
by  abstracting  water  from  the  acid.  Like  other  acids,  acetic 
acid  contains  hydroxyl,  as  will  be  shown  below.  It  may  hence 
be  represented  thus  :  C2H3O.OH.  The  part  C2H30  is  known  as 
acetyl.  Now  when  water  is  abstracted  from  the  acid,  the 
change  takes  place  as  represented  in  this  equation :  — 


SUBSTITUTION-PRODUCTS    OF    ACETIC    ACID  63 

C2H3O.OH)      C2H30 
C2H3O.OHS'=:C2H30> 

Hence,  according  to  this,  acetic  anhydride  appears  as  the  oxide 
of  acetyl,  while  the  acid  itself  is  the  hydroxide. 

It  is  prepared  by  treating  sodium  acetate  with  acetyl  chlo- 
ride :  — 

C2H3O.ONa  +  CICjHjO  =  (C2H30)20  +  NaOl. 

Acetic  anhydride  is  a  colorless  liquid  which  boils  at  137°. 
With  water  it  gives  acetic  acid. 

Acetic  anhydride  may  also  be  used  as  a  test  for  alcoholic 
hydroxyl.  With  methyl  alcohol,  for  example,  it  acts  as  shown 
in  the  following  equation :  — 

CH3OH  +  £2^3°  >  0  =  CH3.  OC2H30  +  CH3COOH. 

Methyl  acetate 

With  all  substances  that  contain  alcoholic  hydroxyl  the  same 
kind  of  action  takes  place. 

Substitution-products  of  acetic  acid.  These  bear  the  same 
relation  to  acetic  acid  that  the  substitution-products  of  marsh 
gas  bear  to  marsh  gas.  They  are  formed  by  the  simple  sub- 
stitution of  a  halogen,  etc.,  for  hydrogen.  Only  three  of  the 
four  hydrogen  atoms  of  acetic  acid  are  capable  of  direct 
replacement.  The  fourth  is  the  one  to  which  the  acid  prop- 
erties are  due.  Hence  the  substitution-products  are  acid.  The 
best  known  of  these  products  are  the  chlor-acetic  acids  which 
are  made  by  treating  the  acid  with  chlorine.  They  are 
mono-chlor-acetiCj  di-chlor-acetic,  and  tri-chlor-acetic  acids.  Their 
formation  is  represented  by  the  following  equations :  — 

C2H3O.OH  +  C12  =  C2H2C10.0H  +  HC1 ; 
C2H2C10.0H  +  C12  =  C2HC12O.OH  +  HC1 ; 
C2HC12O.OH  +  C12  =  C2C13O.OH  +  HC1. 

When  treated  with  nascent  hydrogen  they  are   converted 


64  DERIVATIVES   OF  METHANE  AND    ETHANE 

back  into  acetic  acid.  They  yield  salts,  ethereal  salts,  anhy* 
drides,  etc.,  just  the  same  as  acetic  acid  itself. 

Theory  in  regard  to  the  relations  between  the  acids,  alcohols, 
aldehydes,  and  hydrocarbons.  The  reactions  and  methods  of 
formation  of  acetic  acid  enable  us  to  form  a  clear  conception 
of  the  relation  of  its  constituents.  In  the  first  place  the  pres- 
ence of  hydroxyl  is  shown  by  the  reaction  with  phosphorus 
trichloride.  We  hence  have  C2H3O.OH  as  the  formula  repre- 
senting this  idea.  But  several  questions  still  remain  to  be 
answered.  There  is  another  oxygen  atom  to  be  accounted 
for ;  and  the  relations  between  the  hydroxyl  and  this  oxygen 
must  be  determined  if  possible.  The  fact  that  this  second 
oxygen  is  not  readily  replaced  by  chlorine  indicates  that  it  is 
not  present  as  hydroxyl,  and  all  methods  of  testing  for  hy- 
droxyl fail  to  show  its  presence  in  acetyl  chloride.  Hence  we 
may  conclude  that  the  second  oxygen  atom  is  present  as  car- 

O 

II 

bonyl  CO.  This  leads  us  to  the  formula  H  —  C  —  0  —  H  f or  the 
simplest  acid,  or  formic  acid.  Accordingly,  formic  acid  ap- 
pears as  carbonic  acid,  which  is  commonly  represented  by  the 

X)H 

formula  O  =  cf        ,  in  which  one  hydroxyl  has  been  reduced 
XOH 

to  hydrogen.  It  has  already  been  seen  that  this  reduction  can 
be  accomplished  without  difficulty.  Many  other  arguments 
might  be  brought  forward  in  favor  of  the  view  that  the  above 
formulas  express  the  relations  between  formic  and  carbonic 
acids.  Now,  as  acetic  acid  is  the  homologue  of  formic  acid, 
there  is  good  reason  to  believe  that  it  differs  from  the  latter 
in  that  it  contains  methyl  in  place  of  the  hydrogen,  which 
is  in  direct  combination  with  carbon,  and  this  view  is  con- 
firmed by  the  fact  that  acetic  acid  can  be  made  from  sodium 
methyl,  CH3Na,  and  from  methyl  cyanide,  CH3 .  CN.  The  acid 

O 
II 
must  hence   be  represented   by  the  formula  CH6.C-OH   or 


RELATIONS   BETWEEN   COMPOUNDS    OF    CARBON        65 

CO<OH  '     -1-ke  comraon  constituent  of  the  two  acids  is  the 
O 

II 
group  C  —  O  —  H  or  —  CO. OH,  which  is  generally  known  as  car- 

boxyl.  Acetic  acid  is  closely  related  not  only  to  formic  but  to 
carbonic  acid.  It  may  be  regarded  as  carbonic  acid,  C0<;;5,  in 
which  one  hydroxyl  is  replaced  by  the  radical  methyl.  In  a 
similar  way  we  shall  see  that  all  organic  acids  may  be  regarded 
as  derived  either  from  formic  acid  or  from  carbonic  acid. 
Eepresenting  now  the  simplest  hydrocarbon,  alcohol,  aldehyde, 
and  acid,  by  the  structural  formulas  deduced  from  the  facts, 
we  have 


H 

[OH 

f  0 

ro 

C 

H 

r     H 
U  1  H 

C     H 

C     OH. 

1  H 

1  H 

H 

IH 

i. 

v.  -*-•*• 

Marsh  gas 
(Methane) 

Methyl  alcohol 
(Methanol) 

Formic 
•  aldehyde 
(Methanal) 

Formic  acid 
(Methanic  acid) 

Concerning  the  mechanism  of  the  changes  caused  by  oxida- 
tion, but  little  can  be  determined  by  experiment.  We  may  re- 
gard methyl  alcohol  as  the  first  and  simplest  product  of  oxida- 
tion of  marsh  gas.  Starting  with  methyl  alcohol,  we  might 
expect  the  next  change  to  consist  in  the  introduction  of  another 

I  OH 
OTT 
H  .  But  it  has  been  found  that, 
H 

except  under  certain  peculiar  conditions,  one  carbon  atom  can- 
not hold  two  hydroxyls  in  combination,  and  that,  if  such  a 
compound  is  formed,  it  loses  the  elements  of  water,  thus, 

The    result   would    be    the    aldehyde. 

This  kind  of  change  is  illustrated  in  the  formation  of  carbon 
dioxide  from  the  salts  of  carbonic  acid.  Instead  of  getting 


DO  DERIVATIVES    OP   METHANE   AND    ETHANE 

OTT 

the  acid  CO<OH>  which,  we  should  naturally  expect,  we  get 
this  minus  water  :  — 


Now,  when  the  aldehyde  is  oxidized,  another  oxygen  atom  is 
introduced,  and  the  substance  thus  produced  is  an  acid,  or  the 
hydroxyl  hydrogen  can  be  replaced  by  metals,  and  has  in  gen- 
eral the  characteristics  of  acid  hydrogen.  As  soon  as  we  have 
carbon  in  combination  with  oxygen  as  carbonyl,  and  also  with 
hydroxyl,  the  substance  containing  the  combination  is  an  acid. 

f° 

If,  finally,  the  acid  C  1  OH  is  oxidized,  it  is  probable  that  the 

IH 

same  change  takes  place  as  when  the  alcohol  is  oxidized. 
That  is  to  say,  the  hydrogen  is  probably  replaced  by  hydroxyl, 
when  a  compound  containing  two  hydroxyls  in  combination 
with  one  carbon  atom  would  be  the  result.  This  would  be 
ordinary  carbonic  acid.  But  this  breaks  up  into  water  and 
carbon  dioxide,  which,  as  we  know,  are  the  products  of  oxida- 
tion of  formic  acid. 

All  the  many  representatives  of  the  great  classes  of  carbon 
compounds  known  as  the  alcohols,  aldehydes,  and  acids  are 
closely  related  to  the  three  fundamental  substances,  methyl 
alcohol,  formic  aldehyde,  and  formic  acid.  Keplace  one  of  the 
hydrogen  atoms  of  methyl  alcohol  by  a  radical,  and  we  get  a 
new  alcohol,  which  may  be  represented  by  the  formula 
OH 

TT 

f   .    So  also  a  similar  replacement  of  a  hydrogen  atom  in 


R 


formic  aldehyde  gives  another  aldehyde,  C 


0 


H;  and,  finally,  as 


R 
we  have  seen,  the  acids  of  carbon  may  be  represented  by  the 

fo  K 

formulas  C  JOH,  or  R.CO.OH,  or  CO<OH'  w^c^  snow  their 
R 


ETHEREAL    SALTS  67 

relations  to  formic  and  carbonic  acids.  Hereafter,  in  writing 
the  formulas  of  members  of  the  three  great  classes,  the  struc- 
ture will  be  represented  by  writing  the  hydroxyl  group  OH,  the 
aldehyde  group  CHO,  and  the  carboxyl  group  CO.OH  or  C02H, 
separately  from  the  rest  of  the  formula. 

5.  ETHEREAL  SALTS  OR  ESTERS 

Whenever  an  acid  acts  upon  an  alcohol,  the  acid  is  neutralized 
either  wholly  or  partly,  and  a  product  analogous  to  the  salts  is 
formed.  Thus  nitric  acid  and  ethyl  alcohol  give  ethyl  nitrate :  — 

C2H5.OH  +  HN03  =  C2H5.N03  +  H20, 

just  as  nitric  acid  and  potassium  hydroxide  give  potassium 
nitrate.  It  has  been  pointed  out  that  the  radicals,  methyl,  CH3, 
and  ethyl,  C2H5,  take  the  part  of  metals  in  the  ethereal  salts. 
We  can  thus  get  a  series  of  methyl  and  ethyl  salts  with  the 
various  acids. 

As  regards  the  preparation  of  these  compounds,  it  should  be 
remarked  that  the  action  between  an  alcohol  and  an  acid  does 
not  take  place  as  readily  as  that  between  an  acid  and  a  metallic 
hydroxide.  Only  a  few  of  the  strongest  acids  act  directly 
without  aid.  Such,  for  example,  are  nitric  and  sulphuric  acids, 
though  even  the  latter  is  not  completely  neutralized  by  action 
upon  alcohols,  as  has  already  been  seen  in  the  preparation  of 

C1   IT 

ethyl-sulphuric  acid,        5  >  S04,  for  the  purpose  of  making  ether. 
H 

Plainly  ethyl-sulphuric  acid  is  an  acid  ethereal  salt,  analogous 
to  acid  potassium  sulphate.  Both  are  still  acid,  though  both 
are  likewise  salts. 

The  methods  which  may  be  used  for  preparing  ethereal  salts 
are  the  f ollowirfg :  — 

(1)  Treatment  of  an  acid  with  an  alcohol.     This  is  capable 
of  only  very  limited  application,  as  in  the  case  of  a  few  of  the 
strongest  acids. 

(2)  Treatment  of  an  acid  anhydride  with  an  alcohol.     Thus 


68  DERIVATIVES   OF   METHANE  AND   ETHANE 

in  the  case  of  acetic  anhydride  and  ethyl  alcohol  this  reaction 
takes  place  :  — 

=  CH3.COOC2H5  +  CH3.COOH. 

(3)  Treatment  of  the  chloride  of  an  acid  with  alcohol.  This 
has  been  illustrated  by  the  action  of  acetyl  chloride,  C2H3O.C1, 
upon  methyl  alcohol  (see  p.  62)  :  — 


C2H3OC1    +  HO.CH3  =  C2H3O.OCH3  +HC1, 
or  CH3.COC1  +  HO.CH3  =  CH3.COOCH3  +  HC1. 

(4)  Treatment  of  the  silver  salt  of  an  acid  with  a  halogen 
substitution-product   of   a  hydrocarbon.     For  example,  ethyl 
acetate   can  be   made  by  treating   silver  acetate  with  brom- 
ethane  :  — 

CH3.COOAg  +  C2H5Br  =  CH3COOC2H5  +  AgBr. 

This  reaction  is  well  adapted  to  showing  the  relation  between 
the  salt  and  the  ethereal  salt,  and  leaves  no  room  for  doubt  that 
the  two  are  strictly  analogous. 

(5)  Treatment  of  a  mixture  of  an  alcohol  and  an  acid  with 
dry  hydrochloric  acid  gas  or  strong  sulphuric  acid.     The  forma- 
tion of  ethyl  acetate  by  this  method  was  illustrated  in  Experi- 
ment 19,  p.  61.     The  sulphuric  acid  facilitates  the  action  by 
uniting  with  the  alcohol  to  form  ethyl-sulphuric  acid,  which  with 
the  acid  gives  the  ethereal  salt  :  — 


*«>S04  +  CH3.COOH  =  CH3.COOC2H5  +  H2S04. 
±1 

It  is  probable  that  the  hydrochloric  acid  first  acts  upon  the 
acid  forming  the  chloride,  and  that  this  then  acts  upon  the 
alcohol,  forming  the  ethereal  salt  :  — 

CH3.COOH  +  HC1         =  CH3.COC1        +  H20  ; 
CH3.COC1    +  C2H6OH  =  CH3.COOC2H5  +  HC1. 


ETHEREAL  SALTS  69 

Among  the  more  important  ethereal  salts  of  methyl  and  ethyl 
alcohols,  the  following  may  be  mentioned :  — 

Methyl-sulphuric   acid,      jj3>  SO4,   formed   by   mixing 

methyl  alcohol  and  sulphuric  acid.  The  acid  itself,  as  well  as 
its  salts,  is  very  easily  soluble  in  water. 

Ethyl  nitrate,  C2H5NO3,  formed  by  treating  alcohol  with 
nitric  acid.  Unless  precautions  are  taken  in  mixing  these 
reagents,  complete  decomposition  of  the  alcohol  will  take  place, 
and  the  action  will  be  accompanied  by  a  violent  explosion. 

Ethyl-sulphuric  acid,      53>  SO4.   Made  in  the  same  way 

as  the  methyl  compound.  The  acid  and  its  salts  are  easily 
soluble  in  water.  When  boiled  with  water  it  is  decomposed, 
yielding  alcohol  and  sulphuric  acid :  — 

H20  =  H2S04  +  C2H5OH. 
TL 

Ethyl  sulphate,  (C2H5)2SO4,  is  made  by  passing  the  vapor 
of  sulphur  trioxide  into  well-cooled  ether :  — 

(C2H5)20  +  S03  =  (C2H5)2S04. 

Phosphoric  acid  yields  ethyl  phosphate,  (C2H5)3P04,  di-ethyl-phos- 
phoric  add,  (C2H5)2HP04,  and  ethyl-phosphoric  add,  C2H5H2P04. 

There  also  are  similar  derivatives  of  arsenic,  boric,  silicic,  and 
other  mineral  acids. 

Of  the  ethereal  salts  which  the  two  alcohols  form  with  formic 
and  acetic  acids,  methyl  and  ethyl  acetates  are  the  best  known. 
The  methods  of  preparing  them  have  already  been  given. 
They  are  both  liquids  having  pleasant  odors.  This  is  indeed  a 
characteristic  of  many  of  the  volatile  ethereal  salts  of  the  acids 
of  carbon,  and  many  of  the  odors  of  fruits  and  flowers  are  due 
to  the  presence  of  one  or  another  of  these  compounds.  Many 


70  DERIVATIVES    OF   METHANE   AND   ETHANE 

of  them  also  are  used  for  flavoring  purposes  instead  of  the 
natural  substances. 

Experiment  22.  Make  a  mixture  of  15  parts  (150s)  of  ordinary 
concentrated  sulphuric  acid  and  6  parts  (60s)  absolute  alcohol.  Add  to 
it  10  parts  (100s)  sodium  acetate.  Distil  from  a  flask.  Redistil  the  dis- 
tillate. The  ethyl  acetate  thus  formed  boils  at  77°.  What  reactions  take 
place  in  this  case  ? 

Decomposition  of  ethereal  salts.  Salts  of  most  metals  are  de- 
composed when  treated  with  an  alkaline  hydroxide,  as  caustic 
soda  or  caustic  potash,  the  result  being  a  salt  of  the  alkali  and 
the  hydroxide  of  the  replaced  metal,  as  seen  in  the  case  of 
copper  sulphate  and  sodium  hydroxide :  — 

CuS04  +  2  NaOH  =  Cu(OH)2  +  Na2S04. 

So  also  the  ethereal  salts  are  decomposed  when  treated  with  the 
alkalies,  though,  as  a  rule,  not  as  readily  as  salts.  It  is  usually 
necessary  to  boil  the  ethereal  salt  with  the  alkali  when  decom- 
position takes  place,  the  radical,  like  the  metal,  appearing  in 
the  form  of  the  hydroxide  or  alcohol,  and  the  alkali  metal 
taking  its  place.  Thus,  when  ethyl  sulphate  is  treated  with  a 
solution  of  caustic  potash,  this  reaction  takes  place :  — 

(C2H5)2S04  +  2  KOH  =  K2S04  +  2  C2H5.OH ; 

and  when  ethyl  acetate  is  treated  with  caustic  soda,  we  have 
this  reaction :  — 

CH3.GOOC2H5  +  NaOH  =  CH3.COONa  +  C2H5OH. 

Experiment  23.  In  a  500CC  flask  put  200CC  water,  60s  solid  caustic 
potash,  and  20CC  ethyl  acetate.  Connect  with  an  inverted  condenser, 
arranged  as  shown  in  Fig.  8.  Boil  gently  for  half  an  hour.  Now  connect 
the  condenser  with  the  flask  for  distilling,  and  again  boil.  Examine  the 
distillate  for  alcohol.  Acidify  the  contents  of  the  flask  with  sulphuric 
acid,  and  again  distil.  What  passes  over  ? 

All  ethereal  salts  are  decomposed  by  boiling  with  the  caustic 
alkalies.  As  this  decomposition  is  best  known  on  the  large  scale 
in  the  preparation  of  soaps,  it  is  commonly  called  saponification. 


ACETONE  71 

As  will  be  shown,  the  fats  are  ethereal  salts,  and  soap-making 
consists  in  decomposing  these  fats  by  means  of  the  alkalies. 
Hence,  generally,  to  saponify  an  ethereal  salt  means  to  decom- 
pose it  by  means  of  an  alkali  into  the  corresponding  alcohol 
and  the  alkali  salt  of  the  acid  contained  in  it. 


Fig.  8. 

6.   KETONES  OB  ACETONES 

When  an  acetate  is  distilled,  a  liquid  passes  over  which  has 
the  composition  C3H60,  and  a  carbonate  remains  behind.  The 
reaction  has  been  carefully  studied,  and  has  been  shown  to  take 
place  in  accordance  with  the  following  equation:  — 


The  substance  C3H60  is  known  as  acetone.  It  is  the  best 
known  representative  of  a  class  of  compounds  which  are  some- 
times called  acetones,  but  more  commonly  ketones. 

Acetone,  dimethylketone,  propanone,  C3H6O.  —  Thiy 
substance  has  long  been  known  as  a  product  of  the  distillation 
of  acetates.  It  is  contained  in  considerable  quantities  in  the 


72  DERIVATIVES   OF   METHANE   AND   ETHANE 

product  obtained  in  the  distillation  of  wood,  and  can  be  sepa- 
rated from  the  mixture  after  the  removal  of  the  acetic  acid. 
It  also  occurs  in  the  blood  and  in  urine  in  small  quantity. 
In  certain  abnormal  conditions  it  occurs  in  the  urine  in  large 
quantity  as  in  acetonuria  and  in  diabetes  mellitus. 

It  can  be  purified  by  shaking  a  mixture  containing  it  with  a 
concentrated  solution  of  mono-sodium  sulphite.  It  unites  with 
the  salt,  forming  a  compound  analogous  to  that  formed  with 
aldehyde.  The  double  compound  can  be  separated,  and  when 
distilled  with  the  addition  of  potassium  carbonate  acetone 
passes  over. 

Acetone  is  a  colorless  liquid  having  a  penetrating,  pleasant, 
ethereal  odor.  It  boils  at  56.3°.  It  is  a  good  solvent  for  many 
carbon  compounds,  such  as  resins,  fats,  etc.  It  is  used  in  the 
manufacture  of  chloroform  and  iodoform  and  in  gelatinizing 
smokeless  powders. 

Acetone  more  closely  resembles  the  aldehydes  than  any  other 
bodies  thus  far  considered.  It  is  plainly  not  an  acid  nor  an 
alcohol.  It  is  not  an  ethereal  salt,  for  on  boiling  with  an 
alkali  it  does  not  yield  an  alcohol  nor  the  salt  of  an  acid.  On 
the  other  hand,  it  unites  with  the  acid  sulphites  like  the  alde- 
hydes. Further,  when  treated  with  phosphorus  pentachloride 
its  oxygen  is  replaced  by  two  chlorine  atoms  thus  :  — 
C3H60  +  PC16  =  C3H6C12  +  POC13 ; 

and,  when  treated  with  nascent  hydrogen,  it  is-  converted  into  a 
substance  having  alcoholic  properties.  These  facts  lead  to 
the  conclusion  that  the  substance  contains  carbonyl,  CO,  as  the 
aldehydes  do.  This  is  shown  in  the  formula  C2H6CO.  The 
formation  from  calcium  acetate  leads  further  to  the  belief  that 
the  group  C2H6  really  consists  of  two  methyls,  as  the  simplest 
interpretation  of  the  reaction  is  represented  thus :  — 

CHCOO  CH3 

--         ->  • 


According  to  this,  acetone  is  a  compound  of  two  methyl  groups 


ACETONE  73 

and  carbonyl,  or  it  is  carbon  monoxide  whose  two  available 
affinities  have  been  satisfied  by  two  methyl  groups. 

We  can  test  the  correctness  of  this  view  by  means  of  synthe- 
ses. If  it  is  correct,  it  will  be  seen  that  acetone  is  closely  re- 
lated to  acetyl  chloride.  It  is  acetyl  chloride  in  which  the 
chlorine  has  been  replaced  by  methyl :  — 

CH3.CO.C1  CH3.CO.CH3. 

Acetyl  chloride  Acetone 

Now,  when  acetyl  chloride  is  treated  with  zinc  methyl,  Zn(CH3)2, 
it  yields  acetone  according  to  this  equation :  — 

2  CH3.COC1  +  Zn(CH3)2  =  2  CH3.CO.CH3  +  ZnCl2. 

The  relation  between  acetone  and  ordinary  acetic  aldehyde  is 
similar  to  that  of  an  ethereal  salt  to  its  acid ;  that  is,  acetone 
is  aldehyde,  CH3.COH,  in  which  the  hydrogen  has  been  replaced 
by  methyl,  CH3.CO.CH3. 

Like  the  aldehydes,  the  acetone  has  the  power  of  taking  up 
other  substances,  such  as  the  acid  sulphites,  ammonia,  hydro- 
cyanic acid,  hydrogen,  etc.  This  power  is  in  some  way  con- 
nected with  the  relation  of  the  oxygen  to  the  carbon,  which  is 
the  same  in  both  compounds.  Nevertheless,  this  condition  of 
the  oxygen  does  not  always  carry  with  it  the  same  power  as 
seen  in  the  case  of  the  acids  which  also  contain  carbonyl. 

By  reduction  with  nascent  hydrogen,  acetone  yields  an  alcohol 
of  the  formula  C3H80,  known  as  secondary  propyl  alcohol,  which 
when  oxidized  yields  acetone.  In  other  words,  the  relation  be- 
tween this  alcohol  and  acetone  is  much  the  same  as  that  between 
ethyl  alcohol  and  acetic  aldehyde.  But  while  the  aldehyde  by 
further  oxidation  yields  acetic  acid  by  simply  taking  up  one 
atom  of  oxygen,  acetone  is  decomposed  by  oxidizing  agents,  and 
yields  acetic  and  formic  acids.  Towards  oxidizing  agents,  then, 
acetones  (for  it  will  be  shown  that  other  acetones  conduct 
themselves  in  the  same  way)  act  entirely  differently  from  the 
aldehydes.  The  alcohol  above  mentioned  as  related  to  acetone 


74  DERIVATIVES    OF   METHANE   AND    ETHANE 

is  the  simplest  representative  of  a  class  of  alcohols  differing  in 
some  respects  from  the  substances  commonly  called  alcohols. 


The  most  important  representatives  of  six  classes  of  oxygen 
derivatives  of  the  hydrocarbons  have  thus  far  been  treated  of, 
and,  by  the  aid  of  a  study  of  their  chemical  conduct  and  of  the 
methods  that  may  be  used  in  their  preparation,  definite  views 
in  regard  to  the  relations  between  them  have  been  formed. 
In  ordinary  language  these  relations  may  be  briefly  expressed 
thus  :  The  alcohols  are  the  hydroxyl  derivatives  of  the  hydro- 
carbons or  the  hydroxides  of  certain  groups  called  radicals; 
the  ethers  are  the  oxides  of  these  same  radicals ;  the  aldehydes 
are  compounds  consisting  of  carbonyl,  hydrogen,  and  a  radical ; 
the  acids  are  compounds  of  carbonyl,  hydroxyl,  and  a  radical, 
or,  better,  they  are  carbonic  acid  in  which  hydrogen  and 
oxygen,  or  hydroxyl,  have  been  replaced  by  a  radical;  the 
ethereal  salts  are  coinpounds  like  ordinary  metallic  salts,  only 
they  contain  a  radical  in  place  of  the  metal ;  and,  finally,  the 
ketones  are  aldehydes  in  which  the  distinctively  aldehyde 
hydrogen  has  been  replaced  by  a  radical,  or  they  are  com- 
pounds consisting  of  carbonyl  and  two  radicals. 

These  ideas  are  expressed  in  formulas  thus,  E  being  any 
univalent  radical  like  methyl,  CH3,  or  ethyl,  C2H5:  — 

Alcohol     .         .     .    E-O-H. 

Ether E-O-E. 

Aldehyde      .     .    .     E  -  C  -  H. 

II 
0 

Acid E  — C  — 0  — H. 

II 
O 

Ethereal  salt     .     .    Ac  —  0  —  E  (Ac  —  0  —  H  representing  any 

monobasic  acid). 
Ketone  E  -  C  —  E. 


CHAPTER  V 

SULPHUR  DERIVATIVES  OF  METHANE  AND  ETHANE 
1.   MERCAPTANS 

THE  simplest  derivatives  of  methane  and  ethane  containing 
sulphur  are  the  so-called  mercaptans  or  sulphur  alcohols.  They 
can  be  made  by  a  method  similar  to  one  described  under  the 
head  of  Alcohols.  When  a  mono-halogen  derivative  of  a  hydro- 
carbon, as  brom-m ethane,  CH3Br,  is  treated  with  the  hydroxide 
of  a  metal,  as  silver  hydroxide,  AgOH,  an  alcohol  is  formed :  — 

CH3Br  +  AgOH  =  CH3OH  +  AgBr. 

So,  also,  when  a  similar  halogen  derivative  is  treated  with  a 
hydrosulphide  instead  of  a  hydroxide,  a  compound  is  obtained 
which  may  be  regarded  as  an  alcohol  in  which  the  oxygen  has 
been  replaced  by  sulphur :  — 

CH3Br  -f  KSH  =  CH3SH  +  KBr. 
The  compound  is  called  a  mercaptan. 

Ethyl-mercaptan,  C.,H5-SH.  —  This  substance  can  be  pre- 
pared by  treating  iodo-ethane,  C2H5I,  with  an  alcoholic  solu- 
tion of  potassium  hydrosulphide,  KSH;  also  by  distilling  a 
mixture  of  the  concentrated  solutions  of  potassium  ethylsul- 
phate  and  potassium  hydrosulphide :  — 

°2^5  >  S04  +  KSH  =  K2S04  +  C2H5SH. 
K. 

It  is  a  liquid  of  an  extremely  disagreeable  odor;  it  boils  at  36°; 
and  is  difficultly  soluble  in  water. 

The  name  mercaptan  was  given  to  it  on  account  of  its 
action  towards  mercury.  It  readily  forms  a  compound  in  which 
mercury  takes  the  place  of  hydrogen,  (C2H5S)2Hg;  and  the 
name  has  reference  to  this  power  (mercurium  captans).  It 

76 


76  DERIVATIVES   OF   METHANE   AND   ETHANE 

forms  many  other  well-characterized  metallic  derivatives  like 
this  mercury  compound. 

When  the  sodium  compound  of  rnercaptan  is  exposed  to  the 
air,  it  takes  up  oxygen.  So,  also,  when  mercaptan  itself  is 
treated  with  nitric  acid,  it  is  oxMized,  the  product  having  the 
formula  C2H5.S03H.  It  will  thus  be  seen  that,  though  in  com- 
position mercaptan  is  analogous  to  alcohol,  towards  oxidizing 
agents  it  conducts  itself  quite  differently.  In  the  case  of 
alcohol  two  atoms  of  hydrogen  are  replaced  by  one  of  oxygen. 
In  the  case  of  mercaptan  three  atoms  of  oxygen  are  added 
directly  to  the  molecule.  It  will  be  shown  that  this  new  acid, 
which  is  called  ethyl-sulplwnic  acid,  bears  to  sulphuric  acid  a 
relation  similar  to  that  which  acetic  acid  bears  to  carbonic 
acid ;  and  that  it  bears  to  sulphurous  acid  a  relation  similar 
to  that  which  acetic  acid  bears  to  formic  acid. 

When  treated  with  phosphorus  pentachloride  it  yields  a  chlo- 
ride, C2H5.  S02C1;  and,  when  this  is  treated  with  nascent  hydro- 
gen (zinc  and  hydrochloric  acid),  it  is  reduced  to  mercaptan:  — 
C2H5 .  S02C1  +  6  H  =  C2H5 .  SH  +  HC1  +  2  H20. 

2.    SULPHUR  ETHERS 

These  are  compounds  similar  to  the  ethers.  They  contain 
sulphur  in  the  place  of  the  oxygen  of  the  ethers.  Such  are 
methyl  sulphide,  (CH3)2S,  and  ethyl  sulphide,  (C2H5)2S.  These 
are  made  by  treating  brom-  or  iodo-methane  or  ethane  with 
potassium  sulphide :  — 

2  C2H5I  +  K2S  =  (C2H5)2S  +  2  KI ; 

or  by  treating  the  sodium  salt  of  methyl  or  ethyl-mercaptan 
with  methyl  or  ethyl  iodide:  — 

C2H5 .  SNa  +  C2H5I  =  (C2H5)2S  +  NaJ. 

They  are  liquids  with  very  disagreeable  odors.  When  oxi- 
dized they  are  converted  into  sulphones,  two  atoms  of  oxygen 

being  added,  thus  ^5  >  S  +  02  =  ^5  >  S02. 


SULPHONIC   ACIDS  77 

3.  SULPHONIC  ACIDS 

It  was  stated  above,  that  when  mercaptan  is  oxidized  it  is 
converted  into  an  acid  of  the  formula  C2H5  .  S03H,  or  ethyl-sul- 
phonic add.  This  is  the  representative  of  a  large  class  of  sub- 
stances which  are  commonly  made  by  treating  carbon  compounds 
with  sulphuric  acid.  These  sulphonic  acids  can  best  be  studied 
in  connection  with  another  series  of  hydrocarbons.  Under  the 
head  of  Benzene  (which  see)  it  will  be  shown  that,  when  this 
hydrocarbon  is  treated  with  sulphuric  acid,  a  reaction  takes 
place  that  may  be  represented  thus:  — 


C6H6  +        >  So2  =        .  >  S02  +  H20. 


Benzene  Benzene-sulphonic  acid 

The  sulphonic  acid  thus  obtained  can  also  be  made  by  oxi- 
dizing the  corresponding  mercaptan  or  hydrosulphide,  C6H5.  SH. 
Accordingly,  the  sulphonic  acid  appears  to  be  sulphuric  acid  in 
which  a  hydroxyl  has  been  replaced  by  the  radical  C6H5.  Rea- 
soning by  analogy,  which,  fortunately,  is  supported  by  other 
arguments,  we  may  conclude  that  ethyl-sulphonic  acid  formed 
from  ethyl-mercaptan  bears  a  similar  relation  to  sulphuric  acid, 

f-\     TT 

and  corresponds  to  the  formula  ^Q5>^°^  So,  also,  methyl- 
sulphonic  acid  obtained  by  oxidation  of  methyl-mercaptan 
should  be  represented  by  the  formula  ^3  >  SO2  or  CH8  .  S02OH. 

Its  relation  to  sulphuric  acid  is  the  same  as  that  of  acetic  acid  to 
carbonic  acid. 

Another  method  by  which  the  sulphonic  acids  can  be  pre- 
pared consists  in  treating  a  sulphite  with  a  halogen  substitu- 
tion-product. Thus  ethyl-sulphonic  acid  can  be  prepared  from 
potassium  sulphite  and  iodo-ethane  :  — 

C2H5I  + 
or 


78  DERIVATIVES   OF   METHANE   AND   ETHANE 

According  to  this  reaction  the  sulphonic  acids  appear  to  be 
identical  with  the  ethereal  salts  of  sulphurous  acid,  but  they 
do  not  conduct  themselves  like  ethereal  salts.  The  sulphonic 
acids  as  a  class  are,  for  example,  much  more  stable  than  the 
ethereal  salts  as  a  class.  It  would  be  premature  at  this  stage 
to  discuss  fully  the  question  as  to  their  relations.  Whatever 
we  may  call  them,  they  are  closely  related  to  sulphurous  acid, 
and  are  derived  from  it  by  the  substitution  of  a  radical  for 
hydrogen,  just  as  acetic  acid  may  be  regarded  as  derived  from 
formic  acid  by  the  substitution  of  a  radical  for  hydrogen. 
These  relations  are  represented  by  the  following  formulas  :  — 

Carbonic  acid,  C0<^          Sulphuric  acid,  S02<OH 

OH  OH 

Formic  acid,      CO  <  ^         Sulphurous  acid,  S02  <  H 

OH  OH 


Acetic  acid,       CO  <       3     Methyl-sulphonic  acid,  S02  < 

OH 


Any  carbonic )  nr.    .  E  A  ,  -,      .        .,        or.       E 

[•  CO  <  Any  sulphonic  acid,       S02< 

acid,  y  OH  OH 


The  difference  between  -a  sulphonic  acid  and  an  ethereal  salt 
of  sulphuric  acid  should  be  specially  noticed.    Compare  for  this 

purpose  ethyl-sulphuric  acid,  C2>SO2,  and  ethyl-sulphonic 


C*  TT 

acid,     JJQ  >  S02.     Both  are  monobasic  acids,  and  both  contain 

ethyl,  but  there  is  a  difference  of  one  atom  of  oxygen  in  their 
composition.  The  reactions  of  the  substances  are  such  as  to 
lead  to  the  conclusion  that  in  ethyl-sulphonic  acid  the  ethyl 
group  is  directly  connected  with  the  sulphur;  and  that  in 
ethyl-sulphuric  acid  the  connection  is  established  by  means  of 
oxygen.  The  strongest  argument  in  favor  of  this  view  is  per- 
haps that  which  is  founded  on  the  formation  of  the  sulphonic 
acids  by  oxidation  of  the  hydrosulphides  or  mercaptans.  It 
can  hardly  be  doubted  that  in  ethyl-mercaptan  the  sulphur  is  in 


SULPHONIC    ACIDS  79 

direct  combination  with  the  ethyl ;  or,  to  go  still  farther,  that 
it  is  in  combination  with  carbon,  as  represented  in  the  formula 

H 
H3C  —  C  —  S  —  H.     Now,  by  oxidation  of  mercaptan,  three  atoms 

H 

of  oxygen  are  added,  and  the  simplest  view  of  the  reaction 
is  that  the  sulphur  is  left  undisturbed  in  its  relations  to  ethyl, 
but  that  it  has  taken  up  the  oxygen,  as  represented  in  the 
formula  C2H5—  S02.OH.  As  has  been  shown,  the  oxygen  can 
be  removed  again  by  nascent  hydrogen,  and  the  result  is  mer- 
captan.  The  study  of  the  sulphonic  acids  in  their  relations  to 
sulphuric  and  sulphurous  acids  has  been  of  considerable  assist- 
ance in  enabling  chemists  to  form  conceptions  in  regard  to  the 
constitution  of  the  two  latter.  The  view  which  is  forced 
upon  us  by  a  consideration  of  the  reactions  described  above 
is  that  sulphurous  acid  differs  from  sulphuric  acid  in  con- 
taining a  hydrogen  atom  in  place  of  hydroxyl,  as  represented 

OTT  TT 

in  the  formulas  S02<OH  and  S°2<OH;  and,  further,  that  in 

sulphurous  acid  one  hydrogen  is  in  combination  with  sulphur 
and  the  other  with  oxygen. 


CHAPTER  VI 
NITROGEN  DERIVATIVES   OF  METHANE  AND  ETHANE 

THE  simplest  compounds  of  carbon  containing  nitrogen  are 
cyanogen  and  hydrocyanic  acid.  Strictly  speaking,  neither  can 
be  regarded  as  a  derivative  of  a  hydrocarbon,  unless  indeed  hy- 
drocyanic acid  be  regarded  as  marsh  gas,  in  which  three  hydro- 

(H 

H 
gen  atoms   have   been  replaced  by  one  nitrogen :  C  j       and 

LH 
C  |    .     That,  however,  is  a  mere  matter  of  words,  as  there  is 

nothing  in  the  conduct  of  either  substance,  or  in  the  methods 
of  formation  of  hydrocyanic  acid,  that  would  lead  us  to  suspect 
any  relation  between  them.  Though  cyanogen  and  hydro- 
cyanic acid  are  therefore  not  to  be  considered  as  derivatives  of 
the  hydrocarbons,  they  form  the  starting-point  for  the  prepa- 
ration of  so  many  important  compounds  that  they  and  their 
simpler  derivatives  should  receive  some  attention  at  this  stage. 

Cyanogen,  (CN)2.  —  All  organic  compounds  that  contain 
nitrogen  give  sodium  cyanide  when  ignited  with  sodium.  So, 
also,  potassium  cyanide  is  formed  when  charcoal  containing 
nitrogen  is  heated  with  potassium  carbonate.  Cyanogen  itself 
is  most  readily  made  by  heating  mercuric  cyanide,  Hg(CK)2. 
The  decomposition  that  takes  place  is,  in  the  main,  like  the 
simple  decomposition  of  mercuric  oxide  in  preparing  oxygen  :  — 

Hg(CN)2=Hg  +  (CN)2; 
HgO         =  Hg  +  0. 

But,  in  heating  mercuric  cyanide,  a  black  solid  substance,  para- 
cyanogen,  is  formed,  and  remains  behind  in  the  retort.  It  has 

80 


HYDROCYANIC   ACID  81 

the  same  composition  as  cyanogen,  and  although  its  molecular 
weight  is  not  known,  it  is  presumably  a  polymeric  form  of 
cyanogen. 

Cyanogen  (from  KWXVOS,  blue)  owes  its  name  to  the  fact  that 
several  of  its  compounds  have  a  blue  color.  It  is  a  colorless 
gas,  which  is  easily  soluble  in  water  and  alcohol,  and  is  extremely 
poisonous.  It  burns  with  a  purple-colored  flame. 

In  aqueous  solution,  cyanogen  soon  undergoes  change,  and  a 
brown  amorphous  body  is  deposited.  The  solution  contains 
hydrocyanic  acid,  oxalic  acid,  ammonia,  carbon  dioxide,  and 
urea. 

The  compounds  containing  the  cyanogen  group,  CN,  may  be 
compared  with  those  containing  the  halogens.  In  them  the 
cyanogen  group  plays  the  same  part  as  the  halogen  atom  in  the 
halides.  Thus  we  have :  — 

AgCl  AgCN 

KC1  KCN 

FeCl2  Fe(CN)2 
etc.  etc. 

Hydrocyanic  acid,  HON.  —  This  acid,  which  is  commonly 
called  prussic  acid,  occurs  in  nature  in  amygdalin  in  combina- 
tion with  other  substances,  in  bitter  almonds,  the  leaves  of  the 
cherry,  laurel,  etc.  It  is  prepared  by  decomposing  metallic 
cyanides  with  hydrochloric  acid,  as  represented  in  the  equa- 

KCN  +  HC1  =  KC1  +  HON. 
It  can  also  be  made  by  treating  chloroform  with  ammonia :  — 

CHCls  +  NHg    =HCN       +3HC1, 
or  CHC13  +  5  NH3  =  NH4.CN  +  3  NH4C1. 

It  is  a  volatile  liquid,  boiling  at  26.5°,  which  solidifies  at  — 15°. 
It  has  a  very  characteristic  odor,  suggesting  bitter  almonds.  It 
is  extremely  poisonous.  It  dissolves  in  water  in  all  proportions, 
and  it  is  this  solution  that  is  known  as  prussic  acid.  Pure 


82  DERIVATIVES    OF    METHANE    AND    ETHANE 

hydrocyanic  acid  does  not  suffer  decomposition  when  kept. 
When  water  or  ammonia  is  present,  it  decomposes  and  gives 
ammonia,  formic  acid,  oxalic  acid,  and  a  brown  substance.  A 
small  quantity  of  a  mineral  acid  prevents  this  decomposition. 
By  boiling  with  alkalies  or  acids  it  is  converted  into  formic 
acid  and  ammonia  (see  p.  57). 

Hydrocyanic  acid  can  be  detected  by  the  fact  that  when  its 
solution  is  treated  with  an  excess  of  caustic  potash,  and  a 
solution  containing  a  ferrous  and  a  ferric  salt  is  added,  and  the 
mixture  boiled,  a  precipitate  of  Prussian  blue  is  formed  when 
the  mixture  is  acidified ;  or,  by  adding  yellow  ammonium  sul- 
phide to  its  solution,  evaporating  to  dryness,  and  then  adding  a 
drop  of  a  solution  of  ferric  chloride.  If  hydrocyanic  acid  was 
present,  the  solution  turns  a  deep  blood-red  in  consequence  of 
the  formation  of  ferric  sulpho-cyanate. 

Cyanides.  —  Hydrocyanic,  like  hydrochloric  acid,  forms  a 
series  of  salts,  which  are  called  the  cyanides.  The  cyanides  of 
the  alkali  metals  and  of  mercury  are  soluble  in  water.  The 
cyanides  of  the  heavy  metals  have  a  marked  tendency  to  form 
double  cyanides,  and  those  double  cyanides  which  contain  an 
alkali  metal  are  soluble  in  water.  Hence,  the  precipitates 
formed  by  potassium  cyanide,  in  solutions  containing  the  heavy 
metals,  are  dissolved  by  excess  of  the  cyanide. 

Potassium  cyanide,  KCN.  —  When  anhydrous  potassium 
ferrocyanide  is  ignited,  potassium  cyanide  is  formed  according 
to  this  equation :  — 

K4Fe(CN)G  =  4  KCN  +  FeC2  +  N2. 

Plainly  only  two-thirds  of  the  cyanogen  is  thus  obtained  in  the 
form  of  the  potassium  salt.  In  order  to  obtain  a  larger  yield 
of  cyanide  it  has  been  customary  to  melt  together  potassium 
carbonate  and  ferrocyanide.  The  reaction  that  takes  place  is 
represented  thus :  — 

K4Fe(CN)6  +  K2C03  =  5  KCN  +  KCNO  +  CO.  +Fe. 


POTASSIUM   FERROCYANIDE  83 

The  product  contains  potassium  cyanate.  Potassium  cyanide, 
free  from  the  cyanate,  but  containing  sodium  cyanide,  is  now 
made  on  the  large  scale  by  heating  together  dehydrated  potas- 
sium ferrocyauide  and  metallic  sodium  :  — 

K4Fe(CN)6  +  2  Na  =  4  KCN  +  2  NaCN  +  Fe. 

Potassium  cyanide  is  a  violent  poison.  It  dissolves  easily  in 
water.  When  the  solution  is  boiled,  ammonia  and  potassium 
formate  are  formed.  The  solution  has  an  alkaline  reaction 
due  to  hydrolysis  :  — 

KCN  +  H20  =  HCN  +  KOH. 

It  is  decomposed  by  carbon  dioxide  and  hence  when  exposed 
to  the  air  it  has  the  odor  of  hydrocyanic  acid.  It  precipitates 
cyanides  from  the  solutions  of  almost  all  metallic  salts.  When 
added  in  excess  it  dissolves  the  precipitates,  forming  soluble 
double  cyanides.  A  solution  of  potassium  cyanide  has  the 
power  to  dissolve  gold  from  powdered  gold  ores  and  it  has 
come  into  extensive  use  for  this  purpose. 

Among  the  best-known  double  cyanidets  are  the  two  salts, 
potassium  ferrocyanide  and  potassium  ferricyanide.  The  former 
is  commonly  called  yellow  prussiate  of  potash,  and  the  latter  red 
prussiate  of  potash. 

Potassium  ferrocyanide,  4  KCN.Pe  (CN)2  +  3H2O.  — 
This  is  made  on  the  large  scale  by  melting  together,  in  iron 
vessels,  refuse  animal  substances  (i.e.,  organic  matter  contain- 
ing nitrogen)  with  potassium  carbonate  and  iron.  The  mass 
is  treated  with  water,  and  the  salt  thus  extracted  then  purified 
by  crystallization. 

It  crystallizes  in  large,  lemon-yellow,  monoclinic  plates, 
soluble  in  about  four  parts  of  water  at  15°. 

Experiment  24. 1  Make  a  mixture  of  8  parts  (100s)  dehydrated 
potassium  ferrocyanide  and  3  parts  (60=)  dry  potassium  carbonate.  Fuse 

1  Experiments  24  and  26  may  be  postponed  until  urea  is  taken  up,  when  they  may  be 
combined  with  the  artificial  preparation  of  urea. 


84  DERIVATIVES   OF   METHANE   AND   ETHANE 

in  an  iron  crucible,  at  a  low  red  heat,  until  a  specimen  taken  out  and 
placed  on  a  stone  is  white  when  solid.  Then  pour  out  on  a  flat,  smooth 
stone,  and  afterwards  break  up  and  put  in  a  dry  bottle. 

When  treated  with  dilute  sulphuric  acid,  the  ferrocyanide 
yields  hydrocyanic  acid  thus :  — 

2[4  KCKFe  (ON)  J  +  3  H2S04 

=  6  HCN  +  2[KCN.Fe(CN)  J  +  3  K2S04. 

This  reaction  is  the  one  actually  made  use  of  for  the  prepara- 
tion of  hydrocyanic  acid. 

Potassium  ferrocyanide  is  the  starting-point  in  the  prepara- 
tion of  all  compounds  containing  cyanogen. 

Potassium  ferricyanide,  3KCN.Fe(CN)3.— This  salt, 
known  as  red  prussiate  of  potash,  is  prepared  by  oxidizing  the 
ferrocyanide)  either  by  means  of  chlorine  or  of  potassium 
permanganate. 

Experiment  25.  Dissolve  50s  of  potassium  ferrocyanide  in  750CC  of 
cold  water.  Into  this  pour  slowly  a  cold  solution  of  7s  of  potassium 
permanganate  in  750CC  of  water.  The  oxidation  is  complete  when  a  drop 
added  to  ferric  chloride  gives  a  brownish-red  color,'  but  no  precipitate. 
Heat  for  one  hour  on  the  water-bath,  filter  and  evaporate  to  crystalliza- 
tion. 

Potassium  ferricyanide  is  easily  soluble  in  water,  and  crys- 
tallizes from  its  concentrated  solutions  in  large,  dark-red, 
orthorhornbic  prisms. 

In  alkaline  solutions  it  is  an  excellent  oxidizing  agent. 
Reducing  agents,  such  as  hydrogen  sulphide,  sodium  thiosul- 
phate  (hyposulphite),  etc.,  convert  it  into  the  yellow  salt. 

(1)  Prussian  blue  or  TurnbuWs  blue,  and  (2)  soluble  Prus- 
sian blue  are  complex  double  cyanides  of  iron  represented  by 
the  formulas 

(1)  3  Fe(CN)2.2  Fe(CN)3  or  Fe3''[Feff'(C'.tf)6]2''',  and 

(2)  KCN.Fe(CN),.Fe(CN)2or  KFe'"[Fe"(CN)6]iv,  respectively. 


CYANIC   ACID  85 

For  a  full  account  of  the  many  compounds  of  the  metals  and 
cyanogen,  the  student  is  referred  to  larger  works. 

Cyanogen  chlorides.  —  When  chlorine  is  allowed  to  act 
upon  cyanides  or  dilute  hydrocyanic  acid,  a  volatile  liquid  is 
formed  which  has  the  composition  represented  by  the  formula 
CNC1.  It  boils  at  15.5°,  and  its  vapor  acts  upon  the  eyes, 
causing  tears.  It  is  known  as  liquid  cyanogen  chloride  to  dis- 
tinguish it  from  solid  cyanogen  chloride.  The  latter  has  the 
formula  (CN)3C13,  and  is  formed  by  treating  anhydrous  hydro- 
cyanic acid  with  chlorine  in  direct  sunlight.  The  liquid 
variety  is  partially  transformed  into  the  solid  when  kept  in 
sealed  tubes. 

Similar  compounds  of  cyanogen  with  bromine  and  iodine  are 
known. 

Cyanic  acid,  NCOH.  —  When  a  cyanide  of  an  alkali  is 
treated  with  an  oxidizing  agent,  it  takes  up  oxygen  and  is  con- 
verted into  a  cyanate :  — 

NCK  +  0  =  NOOK. 

Experiment  26.1  Dehydrate  slowly  125«  potassium  ferrocyanide  in 
an  iron  pan  on  a  gas  stove ;  powder  the  dried  salt  and  heat  gently  1  to  2 
hours.  Fuse  75s  potassium  bichromate,  cool,  powder  finely,  and  mix 
thoroughly  with  the  ferrocyanide.  Bring  the  warm  mixture  in  small 
portions  with  an  iron  spoon  into  a  shallow  iron  pan  which  is  heated  suf- 
ficiently to  cause  the  powder  to  glow  and  turn  black.  Stir  rapidly  during 
the  reaction.  Powder  the  porous  mass,  bring  it  while  still  warm  into  a 
mixture  of  450CC  of  80  per  cent  alcohol  and  50CC  methyl  alcohol  in  a  litre 
balloon-flask  and  heat  to  boiling  in  a  water-bath.  The  water  in  the  bath 
should  be  boiling  and  the  alcohol  warm  when  the  mixture  containing  the 
cyanate  is  added.  Boil  for  five  minutes ;  allow  the  undissolved  part  to 
settle  and  pour  the  clear  solution  through  a  plaited  filter  into  a  beaker 
standing  in  ice-water.  The  potassium  cyanate  separates  as  a  heavy  white 
crystalline  powder.  Shaking  the  flask  in  ice-water  hastens  the  crystal- 
lization. Let  the  salt  settle.  With  the  mother-liquor  repeat  three  times 
without  delay  the  extraction  of  the  black  mass,  boiling  ten  minutes  each 

»  See  Note,  p.  88. 


86  DERIVATIVES   OF  METHANE   AND  ETHANE 

time.  With  the  aid  of  a  pump,  filter  each  portion  as  soon  as  obtained ; 
wash  the  united  portions  with  ether;  and  dry  in  a  desiccator  over  sul- 
phuric acid.  The  ;ferrocyanide  must  be  anhydrous  and  the  work  must 
be  done  rapidly.  The  hot  alcoholic  solution  must  be  cooled  rapidly  to 
prevent  decomposition  of  the  cyanate.  Keep  the  cyanate  for  Experiment 47. 

Cyanic  acid  is  readily  decomposed  by  water  yielding  ammo- 
nia and  carbon  dioxide :  — 

NCOH  +  H20  =  NH3  +  C02. 

The  potassium  salt  is  easily  soluble  in  water,  but  is  decom- 
posed by  it,  yielding  ammonia  and  potassium  bicarbonate :  — 

NOOK  +  2  H20  =  KHC03  +  NH3. 

The  most  interesting  salt  of  cyanic  acid  is  ammonium  cyanate, 
NCO.NH4.  It  can  be  made  by  adding  ammonium  sulphate  to 
a  solution  of  the  potassium  salt.  It  is  easily  soluble  in  water; 
but,  if  allowed  to  stand  in  solution,  or  if  its  solution  is  heated, 
it  is  completely  transformed  into  urea,  which  is  isomeric  with  it. 
The  interest  connected  with  this  transformation  was  referred 
to  in  the  introductory  chapter  (p.  1).  It  will  be  treated  of 
more  fully  under  urea. 

Cyanuric  acid,  C3N3H3O3+ 2  H2O. —  This  acid  bears  a  re- 
lation to  cyanic  acid  similar  to  that  which  solid  cyanogen  chlo- 
ride, (CN)3C13,  bears  to  the  liquid  variety.  It  is  made  by 
treating  the  solid  chloride  with  water,  and  also  by  heating 
urea.  It  is  a  crystallized  substance. 

Sulpho- cyanic  acid,  NOSH.  —  Just  as  the  cyanides  of  the 
alkalies  take  up  oxygen  and  are  converted  into  cyanates,  so  also 
they  take  up  sulphur  and  are  converted  into  sulpho-cyanates : — 

CNK  +  S  =  NCSK. 

Potassium 
sulpho-cyanate 

Experiment  27.  Mix  46s  dehydrated  potassium  ferrocyanide  with 
17«  dehydrated  potassium  carbonate,  32s  sulphur,  and  2s  powdered  char- 
coal. Fuse  the  mixture  in  an  iron  pan  on  a  gas  stove  until  the  mass  has 


SULPHO-CYANIC   ACID  87 

become  liquid,  and  a  sample  no  longer  precipitates  Prussian  blue  when 
added  to  a  solution  of  ferric  chloride,  but  turns  the  solution  blood-red :  — 

K4Fe  (CN)6  +  K2C03  +  8  S  =  6  KCNS  +  FeS2  +  C02  +  0. 

The  oxidation  of  the  sulphur  is  prevented  by  the  charcoal.  Pour  the  fused 
mass  on  an  iron  plate,  break  it  up  into  a  coarse  powder,  and  bring  it  into 
a  flask  with  250CC  alcohol.  Boil  with  a  return  condenser  for  ten  minutes, 
and  finally  filter  the  hot  solution,  which  contains  only  sulpho-cyanate.  On 
cooling,  the  salt  crystallizes  in  long  colorless  prisms.  Pour  off  the  mother- 
liquor,  and  use  it  to  extract  the  residue  again  for  a  second  crystallization. 
Evaporation  of  the  mother-liquor  will  yield  a  third  crystallization.  The 
dried  crystals  should  be  preserved  in  well-stoppered  bottles,  as  the  salt  is 
very  hygroscopic. 

Potassium  sulpho-cyanate  crystallizes  in  long  striated  prisms 
without  water  of  crystallization.  It  is  deliquescent.  When 
dissolved  in  water  the  temperature  sinks  markedly.  When  100 
parts  of  water  of  10.8°  are  mixed  with  150  parts  of  the  salt,  the 
temperature  sinks  to  —  23.7°.  By  evaporation  of  the  solution, 
the  salt  can  be  recovered. 

Experiment  28.  Dissolve  some  potassium  sulpho-cyanate  in  water, 
and  note  the  temperature  before  and  after  introducing  the  salt. 

Ammonium  sulpho-cyanate,  NCS.NH4.  This  salt  is  most 
easily  prepared  by  treating  carbon  bisulphide  with  concen- 
trated alcoholic  ammonia:  — 

CS2  +  4  NH3  =  CNS.NH4  +  (NH4)2S. 

Experiment  29.  Mix  240CC  strong  aqueous  ammonia,  240CC  alcohol, 
and  60s  carbon  bisulphide.  Allow  the  mixture  to  stand  for  one  or  more 
days.  Then  distil  down  to  one-third  of  the  original  volume,  arid  filter 
while  still  hot  the  solution  left  in  the  flask.  On  cooling,  ammonium 
sulpho-cyanate  will  crystallize  out. 

The  salt  crystallizes  in  plates.  It  melts  at  130°-140°,  and 
at  this  temperature  is  partly  transformed  into  the  isomeric 
substance  sulpho-urea.  (Analogy  to  transformation  of  ammo- 
nium cyanate.) 

Having  thus  dealt  with  some  of  the  more  important  simpler 
cyanogen  compounds,  let  us  now  return  to  the  nitrogen  de* 


88  DERIVATIVES    OF   METHANE   AND   ETHANE 

rivatives  of  the  hydrocarbons.  For  convenience,  these  may  be 
divided  into  three  classes :  — 

(1)  Those  which  are  related  to  cyanogen  ; 

(2)  Those  which  are  related  to  ammonia; 

(3)  TJiose  which  are  related  to  nitric  acid. 

CYANIDES 

Methyl  cyanide,  CH3.CN.  — This  compound  is  formed  by 
distilling  a  mixture  of  potassium  methyl-sulphate  and  potas- 
sium cyanide:  — 

S04  +  KCN  =  K2S04  +  CH3CN 

It  is  a  liquid  boiling  at  82°. 

According  to  the  method  of  preparation,  it  must  be  regarded 
as  an  ethereal  salt  of  hydrocyanic  acid,  containing  methyl  in 
the  place  of  the  potassium  of  the  potassium  salt. 

Ethyl  cyanide,  C2H5.CN. — Formed  like  the  methyl  com- 
pound. Also  by  heating  chlor-ethane  with  potassium  cya- 
nide :  — 

C2H5C1  +  KCN  =  C2H6.CN  +  KC1. 

It  is  a^liquid  boiling  at  98°. 

The  two  most  characteristic  reactions  of  these  cyanides  are 
(1)  that  which  is  effected  by  caustic  alkalies,  and  (2)  that 
effected  by  nascent  hydrogen. 

When  methyl  cyanide  is  treated  with  caustic  potash,  it  yields 
potassium  acetate  and  ammonia :  — 

CH3.CN  +  H20  +  KOH  =  CH3.C02K  +  NH3. 

This  reaction  is  strictly  analogous  to  that  which  takes  place 
with  hydrocyanic  acid,  yielding  formic  acid  (see  p.  57).  In 
the  same  way  ethyl  cyanide  yields  an  acid  of  the  formula 


ETHYL   CYANIDE  89 

C3H602  (or  C2H5 .  C02H).  Thus,  by  making  a  cyanide,  we  have 
it  in  our  power  to  make  an  acid  containing  the  same  number  of 
carbon  atoms. 

This  reaction,  therefore,  makes  it  possible  to  pass  from  an 
alcohol  to  an  acid  containing  one  atom  of  carbon  more  than 
the  alcohol  contains.  It  has  been  of  great  service  in  the  study 
of  the  compounds  of  carbon. 

NOTE  FOR  STUDENT.  —  Show  how,  by  starting  with  methyl  alcohol, 
acetic  acid  may  be  made  by  passing  through  the  cyanide. 

There  are  two  ways  in  which  the  cyanogen  group  can  be 
linked  to  methyl  in  methyl  cyanide ;  viz.,  either  by  the  carbon 
atom,  as  represented  in  the  formula  H3C  —  C  =  N,  or  by  the 
nitrogen  atom,  as  represented  thus,  H3C  —  N  =  C.  The  ease 
with  which  the  nitrogen  is  separated  from  the  compound,  leav- 
ing the  two  carbon  atoms  united,  as  shown  in  the  reaction  with 
caustic  potash,  naturally  leads  to  the  conclusion  that  the  former 
view  is  the  correct  one.  If  it  is  correct,  it  would  appear  to 
follow  that  in  potassium  cyanide  the  potassium  is  in  combi- 
nation with  carbon,  as  represented  in  the  formula  K  —  C  =  N, 
and  further  that  in  hydrocyanic  acid  the  hydrogen  is  in  combi- 
nation with  carbon,  as  shown  thus,  H  —  C  =  N. 

In  consequence  of  the  close  relation  existing  between  the 
cyanides  and  the  acids,  the  former  are  often  called  the  nitriles 
of  the  acids.  Thus  methyl  cyanide,  which  is  converted  into 
acetic  acid  by  boiling  with  caustic  potash,  is  called  the  nitrile 
of  acetic  acid,  or  aceto-nitrile.  In  the  same  way  hydrocyanic 
acid  itself  may  be  regarded  as  the  nitrile  of  formic  acid,  or 
formo-nitrile. 

When  methyl  cyanide  is  treated  with  nascent  hydrogen, 
it  is  converted  into  a  substance  which  closely  resembles  am- 
monia, known  as  ethyl-amine.  It  will  be  shown  to  bear  to 

fC2H6 

ammonia  the  relation  indicated  by  the  formula  N 4  H     ;  i.e.,  it 

|H 


90  DERIVATIVES   OF  METHANE   AND   ETHANE 

is  ammonia  in  which  one  hydrogen  has  been  replaced  by  ethyl. 
The  reaction  may  be  represented  by  the  equation  :  — 

•C2H5 
-f  4  H  =  H3C  -  H2C  -  NH2 


orN  H 

IH 

This  transformation  strengthens  the  conclusion  already  reached, 
that  the  two  carbon  atoms  in  methyl  cyanide  are  directly  united. 
If  this  were  not  the  case,  it  is  difficult  to  see  how  a  compound 
containing  ethyl  in  "which  the  two  carbon  atoms  are  unques- 
tionably united,  could  be  formed  so  easily  from  it. 

Just  as  methyl  cyanide  yields  ethyl-amine  when  treated  with 
nascent  hydrogen,  so  hydrocyanic  acid  yields  methyl-amine, 

[CH3 

rCH3 


The  amines,  or  substituted  ammonias,  will  be  treated  of 
more  fully  hereafter. 

ISOCYANIDES    OR    CARBAMINES 

If,  in  making  an  ethereal  salt  of  hydrocyanic  acid  from  a  salt, 
the  silver  salt  is  used,  a  compound  is  obtained  having  the  same 
composition  as  the  cyanide,  but  differing  very  markedly  from  it. 
The  substance  thus  obtained  is  called  an  isocyanide  or  carbamine. 

Ethyl  isocyanide  or  ethyl  carbamine,  C2H5NC.  —  This 
compound  is  obtained  when  silver  cyanide  and  iodo-ethane  are 
heated  together :  — 

C2H5I  +  AgffC  =  C2H5NC  +  Agl. 

It  is  also  formed  when  chloroform  and  ethyl-amine  (see  above) 
are  brought  together :  — 

fC2H5 

CHC13  +  N  H     =  C2H5NC  +  3  HC1. 
H 


ETHYL  ISOCYANIDE  91 

It  is  a  liquid  boiling  at  78.1°.  It  is  characterized  by  an  ex- 
tremely disagreeable  odor.  The  methyl  compound  obtained  by 
the  same  method  boils  at  59.6°,  but  otherwise  has  properties 
almost  identical  with  those  of  ethyl  isocyanide. 

The  reactions  of  these  substances  are  quite  different  from 
those  of  the  cyanides.  They  are  decomposed  only  with  great 
difficulty  by  the  caustic  alkalies  ;  but,  when  treated  with  dilute 
hydrochloric  acid,  they  undergo  an  interesting  change,  which 
is  represented  by  the  following  equation  in  the  case  of  the 
methyl  compound  :  — 

CH3 .  NO  +  2  H20  =  CH3  -  NH2  +  H.C02H. 

Methyl  amine          Formic  acid 

This  reaction  indicates  that  in  the  isocyanides  the  cyanogen 
group  is  united  to  the  radical  by  means  of  nitrogen,  as  repre- 
sented by  the  formula  H3C  —  N  —  C.  This  is  probably  the 
reason  that  when  they  undergo  decomposition  the  nitrogen 
remains  in  combination  with  the  radical,  while  the  carbon  of 
the  cyanogen  group  passes  out  of  the  compound.  The  conduct 
of  ethyl  isocyanide  is  represented  by  the  equation :  — 

C2H5.NC  +  2  H20  =  C2H5  -  NH2  +  H.C02H. 

The  reactions  of  the  cyanides  and  of  the  isocyanides,  and 
the  conclusions  drawn  from  them,  admirably  illustrate  the 
methods  used  in  determining  the  structure  of  compounds  of 
carbon;  and  they  are  especially  valuable,  as  the  connection 
between  the  facts  and  the  conclusions,  as  expressed  in  the 
formulas,  can  be  traced  so  clearly. 

The  fact,  that  the  silver  salt  of  hydrocyanic  acid  yields  iso- 
cyanides, while  the  potassium  and  other  salts  yield  cyanides 
with  the  halogen  derivatives  of  the  hydrocarbons,  leads  to  the 
suspicion  that  in  silver  cyanide  the  metal  may  be  in  combina- 
tion with  nitrogen  and  not  with  carbon,  while  in  the  potassium 
salt  it  may  be  in  combination  with  carbon.  Another  possible 
view  is  that  the  cyanides  in  general  have  the  constitution 
MN :  C,  in  which  M  represents  a  univalent  metal.  When 


92  DERIVATIVES    OF   METHANE   AND    ETHANE 

ethyl  iodide  acts  upon  potassium  cyanide,  the  principal  reaction 
is  direct  addition  :  — 

KN  :  C  +  C2H5I  =  KN  :  C  <£2Hs. 

If  the  product  should  break  down  with  elimination  of  potas- 
sium iodide,  the  result  would  be  a  cyanide,  N  •  C.C2H5.  In  the 
case  of  silver  cyanide  the  first  action  may  be  this  :  — • 

C2H5 

AgN :  C  +  C2H5I  =    Ag-^N:C. 
I/ 

The  addition  product  thus  formed  would  then  break  down  into 
silver  iodide  and  the  isocyanide  C2H5N  :  C. 

A  fact  to  be  borne  in  mind  in  connection  with  the  peculiar 
relations  between  the  cyanides  and  the  isocyanides  is  that  it 
has  been  shown  that  some  of  the  isocyanides  are  transformed 
into  cyanides  by  heat. 

Taking  into  consideration  the  facts  presented  by  hydrocyanic 
acid  and  the  cyanides,  it  seems  not  improbable  that  the  acid  is 
capable  of  assuming  both  forms  represented  by  the  formulas 
HN  :  C  and  1ST  •  CH,  and  that  the  salts  are  derived  from  one  or 
the  other  of  these  forms  or  both.  Phenomena  of  this  kind  are 
not  uncommon.  A  compound  that  can  change  from  one  iso- 
meric  form  to  another  or  that  reacts  as  though  it  had  two 
different  formulas  is  called  a  tautomeric  compound.  The  phe- 
nomenon is  called  tautomerism. 

Experiment  30.  The  odor  of  the  isocyanides,  as  has  been  stated,  is 
extremely  disagreeable,  and  in  concentrated  form  it  is  almost  unbearable. 
A  vivid  impression  in  regard  to  this  property  may  be  produced  by  the 
following  experiment.  In  a  test-tube  bring  together  a  little  chloroform, 
aniline,  and  alcoholic  potash.  The  reaction  takes  place  at  once.  It  is 
better  to  perform  the  experiment  out-of-doors,  and  in  such  a  place  that 
the  tube  with  its  contents  can  be  thrown  away  without  molesting  any 
one.  The  aniline  used  is  a  substituted  ammonia  analogous  to  methyl- 
amine,  containing  the  radical  CeHs  in  place  of  methyl.  The  isocyanide 
formed  has  the  formula  CeHg.NC. 


SULPHO-CYANATES  93 

CYANATES  AND  ISOCYANATES 

Two  series  of  compounds  bearing  to  cyanic  acid  much  the 
same  relation  that  the  cyanides  and  isocyanides  bear  to  hydro- 
cyanic acid  may  be  expected. 

The  cyanates  of  the  formula  B,  —  0  —  CN  have  not  yet  been 
obtained. 

In  the  isocyanates  (first  called  cyanates)  the  radical  is 
believed  to  be  united  to  the  cyanogen  by  means  of  nitrogen,  as 
represented  thus,  CH3  —  N  —  CO.  The  isocyanates  are  made 
by  distilling  potassium  cyanate  with  the  potassium  salt  of 
methyl-  or  ethyl-sulphuric  acid.  They  can  be  made  also  by 
bringing  together  the  iodides  of  radicals,  or  iodo-methane  and 
silver  cyanate.  They  are  very  volatile  substances,  which  have 
penetrating  and  suffocating  odors. 

The  isocyanates  readily  yield  substituted  ammonias,  just  as 
the  isocyanides  do  :  — 

.  C2H5  -  N  =  CO  +  H20  =  C2H5  .  NH2  +  C02; 
CH3  -  N  =  CO  +  H20  =  CH3  .  NH2  +  C02. 

S  ULPHO-C  YAN  ATES 

The  ethereal  salts  of  sulpho-cyanic  acid  are  easily  made  by 
distilling  potassium  sulpho-cyanate  and  the  potassium  salt  of 
methyl-  or  ethyl-sulphuric  acid  :  — 


S04  +  KSCN  =  CHgSCN  +  K2S04. 

The  ethyl  compound,  which  is  very  similar  to  the  methyl  com- 
pound, is  a  liquid  boiling  at  142°.    . 

When  boiled  with  nitric  acid,  it  is  oxidized  to  ethyl-sulphonic 
acid.  Now,  it  has  been  shown  above  (see  p.  78),  that  in  ethyl- 
sulphonic  acid  the  ethyl  in  all  probability  is  in  combination 
with  the  sulphur.  It  hence  follows  that,  in  the  sulpho-cyanates 
obtained  from  potassium  sulpho-cyanate,  the  radical  is  also 
in  combination  with  sulphur,  as  indicated  in  the  formula, 
C2H5  —  S  —  GN.  This  view  is  supported  by  the  fact  that 


94  DERIVATIVES    OP   METHANE   AND   ETHANE 

ethyl    sulpho-cyanate    readily    yields    ethyl-mercaptan   when 
treated  with  nascent  hydrogen. 

The  sulpho-cyanates  are  converted  into  iso-sulpho-cyanates 
or  mustard-oils  by  heat. 

ISO-SULPHO-CYANATES  OR  MUSTARD-OILS 

A  number  of  compounds  isomeric  with  the  sulpho-cyanates 
are  known.  The  best-known  member  of  the  class  is  ordinary 
mustard-oil  Hence  they  are  generally  called  mustard-oils. 
The  mustard-oils  are  made  by  means  of  a  series  of  somewhat 
complicated  reactions,  which  it  is  rather  difficult  to  interpret 
without  a  comparison  with  some  similar  reactions  that  take 
place  between  simpler  substances. 

When  dry  ammonia  and  dry  carbon  dioxide  act  upon  each 
other,  so-called  anhydrous  ammonium  carbonate  is  formed. 

This  is  really  the  ammonium  salt  of  carbamic  acid, 
Its  formation  is  represented  thus  :  — 


Now,  remembering  that  carbon  bisulphide  is  similar  to  carbon 
dioxide,  and  that  ethyl-am  ine  is  similar  to  ammonia,  we  can 
readily  understand  the  reaction  which  takes  place  when  these 
two  substances  are  brought  together  :  — 

CS2  +  2  NH2C2H5  =  SC 
The  product  formed  is  the  ethyl-ammonium  salt  of  the  acid 

TV  T-Tf^    T-T 

SC<gH    ;    5,    which    is    called    ethyl-sulpho-carbamic    acid. 

When  the  ethyl-ammonium  salt  is  treated  with  silver  nitrate, 

~\r  wr^1  TT 
the   corresponding   silver   salt,    SC<  5,  is   precipitated. 

Finally,  when  this  is  boiled  with  water,  it  breaks  up,  yielding 
ethyl  mustard-oil,  silver  sulphide,  and  hydrogen  sulphide  :  — 


2  SO  <  5  =  2  SG  -  NC2H5  +  H2S  -f  Ag2S. 


ISO-SULPHO-CYANATES  95 

Ethyl  mustard-oil  is  an  oily  liquid  that  does  not  mix  with 
water.  It  has  a  very  penetrating  odor,  and  acts  upon  the 
mucous  membranes  of  the  eyes  and  nose  in  the  same  way  as 
ordinary  oil  of  mustard. 

Some  of  the  arguments  have  been  stated  which  lead  to  the 
view  that  in  the  sulpho-cyanates  the  radical  is  in  combination 
with  sulphur.  The  reactions  of  the  mustard-oils  lead  just  as 
clearly  to  the  conclusion  that  in  them  the  radical  is  in  com- 
bination with  nitrogen.  In  the  first  place,  they  are  made  from 
the  amines.  Again,  when  heated  with  dilute  mineral  acids, 
ethyl  mustard-oil  is  hydrolyzed,  yielding  ethyl-amine,  carbon 
dioxide,  and  hydrogen  sulphide :  — 

SC  -  NC2H5  +  2  H20  =  C2H5NH2  +  H2S  +  C02. 

And  further,  nascent  hydrogen  converts  it  into  ethyl-amine  and 
formic  thioaldehyde  (i.e.,  formic  aldehyde  in  which  the  oxygen 
has  been  replaced  by  sulphur)  :  — 

SC  -  NC2H5  +  4  H  =  C2H5.NH2  +  H2CS. 

Thus,  as  has  been  shown,  the  sulpho-cyanates  yield  mercaptans 
with  nascent  hydrogen,  while  the  iso-sulpho-cyanates  yield  sub- 
stituted ammonias.  These  facts  point  to  the  relations  ex- 
pressed in  the  formulas,  E.  —  S  —  ON  for  the  sulpho-cyanates, 
and  E,  —  N  —  CS  for  the  iso-sulpho-cyanates  or  mustard-oils. 


In  reviewing  now  the  compounds  of  the  hydrocarbons  which 
are  related  to  cyanogen,  we  see  that  there  are  two  isomeric 
series  of  these,  the  names  and  general  formulas  of  which  are 
given  below :  — 

Cyanides,  E  — C  — N      .     .     .     .  Isocyanides     or' 


Carbainines,    '  " 


3S     orl 

fix  — . 
tines,   J 

Cyanates,  K-O-CN    .     .     .     .  Isocyanates,         K-N-CO 
Sulpho-cyanates,  K—S  —  CN  .     .  Iso-sulpho-cya-  1 

natesorMus4R— N  — CS 

tard-oils. 
Of  these  all  are  known  except  the  cyanates. 


96  DERIVATIVES    OF   METHANE   AND   ETHANE 

SUBSTITUTED  AMMONIAS 

When  brom-ethane  or  a  similar  substitution-product  is 
treated  with  ammonia,  the  reactions  represented  by  the  fol- 
lowing equations  take  place  step  by  step :  — 

C2H5Br  +  NH3  =  NH3(C2H5)Br ; 

C2H5Br  +  NH2(C2H5)  =  NH2(C2H5)2Br ; 
C2H5Br  +  NH(C2H5)2  =  NH(C2H5)3Br ; 
C2H5Br  +  N(C2H5)3     ==  N(C2H5)4Br. 

The  products  thus  formed  are  salts  resembling  ammonium 
salts.  When  the  first  three  are  distilled  with  potassium 
hydroxide  they  are  decomposed,  just  as  ammonium  bromide 
would  be.  Only  instead  of  ammonia  and  potassium  bro- 
mide, the  compounds  ethyl-amine,  NH2.C2H5,  di-ethyl-amine, 
NH(C2H5)2,  and  tri-etliyl-amine,  N(C2H5)3,  are  obtained.  These 
substances  may  be  regarded  as  derived  from  ammonia  by  the 
replacement  of  one,  two,  and  three  of  the  hydrogen  atoms 
respectively  by  ethyl.  The  last  product  of  the  series  of  re- 
actions represented  above  may  be  regarded  as  ammonium 
bromide,  NH4Br,  in  which  all  four  hydrogen  atoms  are  re- 
placed by  ethyl  groups. 

The  decomposition  by  potassium  hydroxide  of  the  first  two 
salts  is  represented  thus  :  — 

NH3(C2H5)  Br  +  KOH  =  NH2(C2H5)  +  KBr  -f  H20 ; 
.  NH2(C2H5)2Br  +  KOH  =  NH(C2H5)2  -f  KBr  +  H20. 

Methyl-amine,  NH2.CH3.  —  This  compound  can  be  pre- 
pared by  treating  iodo-methane  with  ammonia,  the  direct 
product  of  the  reaction  being  methyl-ammonium  iodide, 
NH3(CH3)I:  — 


It  was  first  made  by  treating  methyl  isocyanate,  CH3  —  N  =  CO, 
with  caustic  potash :  — • 

CH3 -  K  -  CO  +  H20  =  NH2.  CH3  +  C02. 


DI-METHYL-AMINE  97 

It  has  been  stated  that  it  is  formed  by  treating  hydrocyanic 
acid  with  nascent  hydrogen  :  — 


It  occurs  in  nature  in  herring  brine,  in  Mercurialis  perennis, 
and  is  one  of  the  products  of  the  distillation  of  animal  matter 
1  as  well  as  of  wood. 

Methyl-amine  is  a  gas  that  is  easily  condensed  to  a  liquid. 
It  smells  like  ammonia  and  fish.  It  burns  with  a  yellow  flame. 
It  is  more  strongly  basic  and  more  soluble  in  water  than  am- 
monia, 1  volume  of  water  at  12.5°  taking  up  1150  volumes  of 
the  gas.  This  solution  acts  almost  exactly  like  a  solution  of 
ammonia  in  water.  It  is  strongly  alkaline.  It  precipitates 
many  metallic  hydroxides  from  solutions  of  their  soluble  salts, 
but,  unlike  ammonia,  it  does  not  dissolve  precipitated  hydrox- 
ides of  nickel,  cobalt,  and  cadmium  when  added  in  excess.  It 
dissolves  aluminium  hydroxide. 

Methyl-amine  forms  salts  with  acids  in  the  same  way  that 
ammonia  does  ;  that  is,  by  direct  addition.  The  action  towards 
nitric  and  sulphuric  acids  takes  place  in  accordance  with  the 
following  equations  :  — 


=  (NH3CH3)N03; 
2  NH2CH3  +  H2S04  =  (NH3CH3)2S04. 

These  salts  are  called  methyl-ammonium  nitrate  and  methyl- 
ammonium  sulphate  respectively. 

Di-methyl-amine,  NH(CH3)2.  —  This  is  formed  by  heating 
iodo-methane  with  alcoholic  ammonia:  — 

2  CH3I  +  2  NH8  =  NH  (CH3)2  .  HI  -f  NH4L 

It  is  formed,  together  with  methyl-amine,  as  a  product  of 
the  distillation  of  wood. 

It  is  a  gas  which  condenses  to  a  liquid  at  +  7.2°.  Its  prop 
erties  are  much  like  those  of  methyl-amine, 


98  DERIVATIVES   OF  METHANE   AND   ETHANE 

Tri-methyl-amine,  N(CH3)3.  —  Tri-methyl-amine  is  formed 
as  one  of  the  products  of  the  treatment  of  iodo-m ethane  with 
ammonia.  It  occurs  widely  distributed  in  nature,  as  in  the 
blossoms  of  the  hawthorn,  the  wild  cherry,  and  the  pear.  It 
is  contained  in  herring  brine,  and  is  a  common  product  of  the 
decomposition  of  organic  substances  that  contain  nitrogen. 
It  is  now  obtained  in  large  quantities  from  the  so-called  "  vin- 
asse."  This  is  the  waste  liquid  obtained  in  the  refining  of 
beet  sugar.  When  the  "vinasse"  is  evaporated  to  dryness, 
and  the  residue  subjected  to  dry  distillation  tri-methyl-amine 
is  given  off.  It  is  collected  as  the  hydrochloric  acid  salt, 
N(CHS)3HC1,  which,  when  heated  with  hydrochloric  acid, 
yields  ammonia  and  chlor-methane  :  — 

N(CH3)3HC1  +  3  HC1  =  3  CH3C1  +  NH4C1. 

The  chlor-methane  is  utilized  for  the  purpose  of  producing  low 
temperatures. 

Tri-methyl-amine  is  a  liquid  boiling  at  3.5°.  It  has  a  strong 
ammoniacal  and  fishy  odor.  It  is  very  soluble  in  water  and 
alcohol,  and  is  a  strong  base. 

The  ethyl-amines  are  very  much  like  the  methyl  compounds, 
and  hence  need  not  be  specially  described. 

When  tri-ethyl-amine  is  brought  together  with  iodo-ethane, 
the  two  unite,  forming  the  compound  tetra-ethyl-ammonium 
iodide,  N  (C2H5)4I,  which  is  to  be  regarded  as  ammonium  iodide, 
in  which  all  four  hydrogen  atoms  have  been  replaced  by  ethyl 
groups.  If  silver  oxide  is  added  to  the  aqueous  solution  of  the 
iodide,  silver  iodide  is  formed,  and  by  evaporation  of  the  liquid 
crystals  of  tetra-ethyl-ammonium  hydroxide,  N(C2H5)4OH,  are 
obtained.  This  is  plainly  the  hypothetical  ammonium  hydrox- 
ide, in  which  the  four  ammonium  hydrogens  have  been  replaced 
by  ethyl.  Its  solution  acts  almost  like  caustic  potash.  It  is 
very  caustic,  attracts  carbon  dioxide  from  the  air,  saponifies 
(see  p.  71)  ethereal  salts,  and  gives  the  same  precipitates  as  caus- 
tic potash.  It  is  so  strong  a  base  that  neither  potassium  nor 


TRI-METHYL-AMINB  99 

sodium  hydroxide  can  separate  it  from  its  salts.  The  reactions 
of  the  substituted  ammonias  above  described  make  it  certain 
that  they  are  closely  related  to  ammonia.  The  methods  of 
formation  also  point  clearly  to  the  same  conclusion.  This 
relation  is  best  expressed  by  the  formulas  above  given. 

Another  method  for  the  formation  of  substituted  ammonias 
in  which  but  one  radical  is  present,  as  ethyl-amine,  NH2.C2H5, 
or  in  general  NH2.R,  consists  in  treating  with  nascent  hydro- 
gen compounds  known  as  mtro-compounds,  which  are  substi- 
tution-products containing  the  group  N02  in  the  place  of 
hydrogen.  Thus,  for  example,  when  nitro-methane,  CH3.N03 
(which  see),  is  treated  with  hydrogen,  the  reaction  that  takes 
place  is  represented  thus  :  — 

CH3.  N02  +  6  H  =  CH3.  NH2  +  2  H20. 


In  connection  with  another  series,  it  will  be  shown  that  this 
reaction  is  a  most  important  one,  from  a  practical  as  well  as 
a  scientific  point  of  view.  It  may  be  said  in  anticipation  that 
the  manufacture  of  aniline,  and  consequently  of  all  the  many 
valuable  dye-stuffs  related  to  aniline,  is  based  upon  this 
reaction. 

Just  as  we  may  look  upon  methyl-amine  and  the  related  com- 
pounds, as  ammonia,  in  which  one  hydrogen  atom  is  replaced  by 
methyl,  so  also  we  may  regard  them,  and  with  equal  right,  as 
marsh  gas,  in  which  hydrogen  has  been  replaced  by  the  group 
or  residue  NH2.  Owing  to  the  frequency  of  the  occurrence  of 
this  group  in  carbon  compounds,  and  for  the  sake  of  simplify- 
ing the  nomenclature,  the  group  has  been  called  the  amino 
group,  and  the  bodies  containing  it  amino-compounds.  Thus 
the  compound  NH2'C2H5  may  be  called  either  ethyl-amine  or 
amino-ethanej  etc. 

Similarly,  those  substituted  ammonias  which  contain  two 
hydrocarbon  residues,  as  di-ethyl-amine,  NH  (G2H5)2,  are  called 
imino-compounds,  and  the  group  NH  the  imino  group.  Sub- 
stituted ammonias  containing  one  hydrocarbon  residue  are 


100  DERIVATIVES   OF   METHANE   AND   ETHANE 

called  primary  ammonia  bases.  Those  containing  two  residues, 
as  di-ethyl-amine,  NH(C2H5)2,  are  known  as  secondary  ammonia 
bases;  and  those  containing  three  residues,  as  tri-ethyl-amine, 
N  (CH3)3,  are  called  tertiary  ammonia  bases. 

Among  the  most  important  of  the  reactions  of  amino-com- 
pounds  or  primary  bases  is  that  which  takes  place  when  they 
are  treated  with  nitrous  acid.  Take  ethyl-amine  as  an  illus- 
tration. In  order  to  understand  what  takes  place  when  this 
compound  is  treated  with  nitrous  acid,  it  is  necessary  to  keep 
in  mind  the  fact  that  the  compound  itself  is  a  modified  ammo- 
nia, and  hence  we  may  expect  that  its  reactions  will  be 
modifications  of  those  which  take  place  with  ammonia.  Thus 
with  nitrous  acid  ammonia  unites  directly  to  form  ammonium 
nitrite  :  — 

+  HN02  = 


So  also  ethyl-amine  forms  ethyl-ammonium  nitrite  :  — 
NH2.C2H5  +  HN02  =  NH3(C2H5).N02. 

Ammonium  nitrite  breaks  up  readily  into  free  nitrogen  and 
water  :  — 

NH4.N02  =  N2  +  H20  +  H20. 

So  also  ethyl-ammonium  nitrite  breaks  up  into  free  nitrogen, 
water,  and  alcohol  :  — 

NH3(C2H5)N02  =  N2  +  H20  +  C2H5.OH. 

The  two  reactions  are  strictly  analogous.  As  in  the  second 
case  we  start  with  a  substituted  ammonia,  we  get  as  a  product 
a  substituted  water  or  alcohol. 

This  reaction  has  been  used  extensively  in  the  preparation 
of  compounds  containing  hydroxyl.  For  ordinary  alcohol, 
as  is  clear,  it  is  not  a  convenient  method  of  preparation  ;  but  it 
will  be  shown  that  there  are  hydroxides  for  the  preparation  of 
which  it  is  by  far  the  most  convenient  method.  The  essential 
character  of  the  transformation  effected  by  it  will  be  best  under- 


NITRO-COMPOUNDS 


stood  by  comparing  the  formulas  of  the^anndjorcompouiid  and/ 
the  alcohol.  We  have  ethyl-amine,  C2H5.NH2,  and  from  it  we 
get  alcohol,  C2H5.OH.  Thus  it  will  be  seen  that  the  trans- 
formation consists  in  replacing  the  amino  group  by  hydroxyl. 

HYDRAZLNE  COMPOUNDS 

There  is  an  important  class  of  compounds,  the  members  of 
which  bear  the  same  relation  to  the  compound  hydrazine,  N2H4, 
(H2N  —  NH2),  that  the  substituted  ammonias  bear  to  ammonia. 
The  reactions  by  which  they  are  prepared  are  somewhat  com- 
plicated, and  cannot  well  be  discussed  at  this  stage.  The  best- 
known  hydrazines  are  those  related  to  the  hydrocarbons  of  the 
benzene  series,  as,  for  example,  phenylhydrazine,  C6H5.NH.NH2. 

NlTRO-COMPOUNDS 

Reference  has  already  been  made  to  a  class  of  compounds  con- 
taining the  group  N02,  and  known  as  nitro-compounds.  They 
are  most  readily  made  by  treating  the  hydrocarbons  with  nitric 
acid.  This  method,  however,  is  not  applicable  to  the  hydro- 
carbons methane  and  ethane  and  their  homologues,  as  these  are 
not  readily  changed  by  nitric  acid.  The  hydrocarbon  benzene, 
C6H6,  is  very  easily  acted  upon  by  nitric  acid,  when  the  reac- 
tion represented  by  the  following  equation  takes  place  :  — 

C6H6  +  HONO,  =  C6H5N02  +  H20. 

The  action  is  like  that  which  takes  place  between  sulphuric 
acid  and  benzene,  which  gives  the  sulphonic  acid  C6H5.S02OH 

or  C^>s°2-    (See  p.  77.)     In  each  case  a  hydroxyl  of  the 

acid  is  replaced  by  a  residue  of  the  hydrocarbon.  The  product 
in  the  case  of  the  dibasic  acid,  sulphuric  acid,  is  itself  still 
acid,  while  the  product  in  the  case  of  the  monobasic  nitric 
acid  is  not  an  acid. 

The  nitro-derivatives  of  methane  have  been  made  by  a  reac- 
tion which  we  should  expect  to  yield  ethereal  salts  of  nitrous 


1G2          EERlVi/i^VES   OF  METHANE   AND   ETHANE 


cidj  namfcty,.  py^re^ting  iodomethane  or  ethane  with  silver 

CH3I  +  AgN02  =  CH3N02  +  Agl. 

The  compound  CH3N02,  which  is  known  as  nitro-methane,  does 
not  conduct  itself  like  the  ethereal  salts  of  nitrous  acid.  Methyl 
nitrite,  CHaO.NO,  can  be  saponified  ;  nitro-methane  cannot. 

NOTE  FOR  STUDENT.  —  Compare  the  reaction  just  referred  to  with  that 
which  takes  place  between  silver  cyanide  and  iodo-methane  ;  and  that 
which  takes  place  between  iodo-ethane  and  potassium  sulphite.  What 
analogy  is  there  to  the  former  and  to  the  latter  ? 

It  has  already  been  stated  that  the  nitro-derivatives  are  con- 
verted by  nascent  hydrogen  into  the  corresponding  amino- 
derivatives  (see  p.  99). 

NOTE  FOR  STUDENT.  —  Write  the  equations  representing  the  reactions 
by  which  methyl  alcohol  can  be  converted  into  methyl-amine  by  means 
of  the  nitro-conipound. 

Nitroform,  CH(NO2)3,  as  the  formula  indicates,  is  the  tri- 
nitro-derivative  of  methane,  or  tri-nitro-methane.  It  is  con- 
verted into  tetra-nitro-methane,  C(N02)4,  when  treated  with  a 
mixture  of  concentrated  sulphuric  and  fuming  nitric  acids. 

Nitro-chloroform,  C(NO2)C13,  called  also  chlorpicrin  and 
nitro-trichlormethane,  is  formed  by  distilling  methyl  or  ethyl 
alcohol  with  common  salt,  saltpetre,  and  sulphuric  acid.  It  is 
formed  from  a  number  of  more  complicated  nitro-compounds, 
as  picric  acid,  by  distilling  them  with  bleaching  powder  or 
hydrochloric  acid  and  potassium  chlorate. 

NlTROSO-   AND    ISONITROSO-COMPOUNDS 

When  a  compound  containing  the  group  CH  is  treated  with 
nitrous  acid,  a  reaction  takes  place,  which  is  represented  thus:  — 

E3CH  +  HO.NO  =  R3C.NO  +  H20. 

The  product  R3C.NO,  which  is  derived  from  the  original  sub- 
stance by  the  substitution  of  the  group  NO  for  a  hydrogen 
atom,  is  called  a  nitroso-compound.  By  oxidation  the  nitroso- 


NITROSO-    AND    ISCXNITROSO-COMPOUNDS  103 

compounds  are  converted  into  nitre-compounds,  and  by  reduc- 
tion they  yield  the  same  products  as  the  corresponding  nitro- 
compounds,  that  is  to  say,  the  amines. 

The  isonitroso-compounds  are  isomeric  with  the  nitroso-com- 
pounds.      They  are  formed  when  acetones  or  aldehydes  are 
treated  with  hydroxylamine,  NH2.OH.     The  reaction  may  be 
represented  thus  :  — 
CH 


CO  +  H2KOH  =  C=N  -  OH  +  H20. 

I  I 

CH3  CH3 

The  hydrogen  of  the  hydroxyl  has  acid  properties.  The 
isonitroso-compounds  are  readily  hydrolyzed  by  hydrochloric 
acid,  yielding,  as  one  of  the  products,  hydroxylamine.  They 
are  generally  called  oximes. 

As  hydroxylamine  reacts  in  this  way  with  all  aldehydes 
and  with  all  ketones,  it  is  a  valuable  reagent  for  compounds 
belonging  to  these  classes. 

Fulminic  acid,  CNOH,  according  to  recent  investigations, 
appears  to  be  an  isonitroso-compound,  and  for  that  reason  finds 
appropriate  mention  in  this  place.  The  principal  compound 
of  fulminic  acid  is  the  mercuric  salt,  C2N202Hg,  commonly 
known  as  fulminating  mercury.  It  is  prepared  by  dissolving 
mercury  in  an  excess  of  strong  nitric  acid,  and  adding  alcohol 
to  the  solution.  It  is  extremely  explosive.  Mixed  with  potas- 
sium nitrate  it  is  used  for  filling  percussion-caps. 

When  fulminating  mercury  is  treated  with  concentrated 
hydrochloric  acid,  it  yields  hydroxylamine  and  formic  acid. 
Fulminic  acid  appears,  therefore,  to  be  an  isonitroso-compound. 
It  is  probably  the  oxime  of  carbon  monoxide,  and  should  be 
represented  by'the  formula  C  =  N  —  OH.  As  will  be  seen, 
fulminic  acid  is  isomeric  with  cyanic  and  cyanuric  acids  (see 
pp.  85  and  86). 


CHAPTER  VII 

DERIVATIVES   OF   METHANE  AND   ETHANE  CONTAINING 
PHOSPHORUS,    ARSENIC,    ETC. 

Phosphorus  compounds.  —  Corresponding  to  the  amines 
or  substituted  ammonias  are  the  phosphines,  which,  as  the  name 
implies,  are  related  to  phosphine,  PH3.  Methyl-phosphine, 
PH2(CH3),  di-methyl-phosphine,  PH(CH3)2,  and  tri-methyl- 
phosphine,  P(CH3)3,  may  be  taken  as  examples. 

These  substances,  like  the  corresponding  amines,  form  salts 
with  acids,  though  not  as  readily.  The  hydroxide,  tetra-etliyl- 
pliosphonium  hydroxide,  P(C2H5)4OH,  is  a  very  strong  base, 
though  not  as  strong  as  the  corresponding  nitrogen  derivative. 

The  phosphines  have  one  marked  property  which  distin- 
guishes them  from  the  amines,  and  that  is  their  power  to  take 
up  oxygen  and  form  acids.  Thus,  ethyl-phosphine,  PH2.C2H5, 
when  treated  with  nitric  acid,  is  converted  into  ethyl-phosphinic 
acid,  PO(C2H5)(OH)2,  a  dibasic  acid,  bearing  to  phosphoric  acid 
the  same  relation  that  a  sulphonic  acid  bears  to  sulphuric  acid. 

NOTE  FOR  STUDENT.  —  What  is  the  relation  ?  What  other  class  of 
acids  bears  the  same  relation  to  carbonic  acid  ? 

Di-ethyl-phosphine,  PH(C2H5)2,  yields  di-ethyl-phosphinic  acid, 
PO(C2H6)2OH,  when  oxidized. 

These  compounds  are  not  commonly  met  with,  and  do  not 
play  a  very  important  part  in  the  study  of  the  compounds  of 
carbon. 

Arsenic  compounds.  —  The  most  characteristic  carbon 
compound  containing  arsenic  is  that  which  is  known  as  cacodyl, 
a  name  given  to  it  on  account  of  its  extremely  disagreeable 
odor  (from  KOIKES,  stinking).  It  is  prepared  by  distilling  a 
mixture  of  potassium  acetate  and  arsenic  trioxide.  The  reac- 

104 


SODIUM   ETHYL  105 

tions  which  take  place  are  very  complicated,  and  many  products 
are  formed.     Chief  among  the  products  is  cacodyl  oxide :  — 

4  CH3.C02K  +  As/)3  =  [(CH3)2As]20  +  2  K2C03  +  2  C02. 

When  treated  with  hydrochloric  acid,  the  oxide  is  converted 
into  the  chloride  (CH8)2AsCl ;  and,  when  the  chloride  is  treated 
with  zinc,  cacodyl  itself  is  produced.  Its  analysis  and  the 
determination  of  its  molecular  weight  lead  to  the  formula 
As2C4H12,  which  in  all  probability  should  be  represented  thus : 

rCH)  As)'     Cacodyl  is  therefore  analogous  to  tetra-methyl- 
hydrazine.     (See  p.  101.) 

NOTE  FOR  STUDENT.  —  In  what  does  the  analogy  consist  ? 

Many  derivatives  of  cacodyl  have  been  made,  but  their  study 
would  hardly  be  profitable  at  this  stage. 

Zinc  ethyl  itself  is  made  by  treating  iodo-ethane,  C2H5I, 
with  zinc  alone  or  with  zinc  sodium.  The  reaction  takes  place 
in  two  stages.  First  by  addition,  a  compound  of  the  formula 

Zn<c  H     is  formed.     When  this  is  distilled,  zinc  ethyl  and 

zinc  iodide  are  formed :  — 

2  Zn  <  *        =  Zn(C2H5)2  +ZnI2. 

^2*15 

It  is  a  liquid  boiling  at  118°.     It  takes  fire  in  the  air,  and  burns 
with  a  white  flame. 

Sodium  ethyl,  C2H5Na,  can  be  obtained  in  combination 
with  zinc  ethyl  by  treating  the  latter  with  sodium.  Both 
these  compounds  have  been  used  to  a  considerable  extent  in 
the  synthesis  of  carbon  compounds,  particularly  the  more  com- 
plex hydrocarbons,  and  they  will  be  frequently  referred  to  in 
the  following  pages. 

NOTE  FOR  STUDENT.  —  What  is  formed  when  sodium  methyl  and 
carbon  dioxide  are  allowed  to  act  upon  each  other  ? 


106          DERIVATIVES   OF   METHANE   AND   ETHANE 

Many  of  the  derivatives,  like  the  above,  are  volatile  liquids. 
Such,  for  example,  are  mercury  ethyl,  Hg(C2H5)2,  aluminium 
ethyl,  A1(C2H5)3,  tin  tetrethyl,  Sn(C2H5)4,  and  silicon  tetrethyl, 
Si(C2H5)4.  The  study  of  these  compounds  has  been  of  assist- 
ance in  enabling  chemists  to  determine  -the  atomic  weights  of 
some  of  the  elements  which  do  not  form  simple  volatile 
compounds. 

Barbier-Grignard  reaction. — When  magnesium  powder 
is  added  to  a  solution  of  an  organic  halide,  such  as  methyl 
iodide,  ethyl  bromide,  etc.,  in  anhydrous  ether,  magnesium 
enters  into  combination  with  the  halide,  forming  a  compound 
that  reacts  easily  with  a  variety  of  substances.  The  reaction 
is  known  by  the  names  of  the  discoverers,  Barbier  and 
Grignard.  A  simple  example  is  that  indicated  below :  — 

CH8I  +  Mg  =  CH,MgI. 
CH3MgI  +  H20  =  CH4  +  IMgOH. 

This  particular  reaction,  as  will  be  seen,  affords  an  easy 
method  of  passing  from  methyl  iodide  to  methane. 

RETROSPECT 

In  the  introductory  chapter  (p.  19)  these  words  were  used  in 
describing  the  plan  to  be  followed:  "Of  the  first  series  of 
hydrocarbons  two  members  will  be  treated  of.  Then  the  de- 
rivatives of  these  two  will  be  taken  up.  These  derivatives  will 
serve  admirably  as  representatives  of  the  corresponding  deriva- 
tives of  other  hydrocarbons  of  the  same  series  and  of  other 
series.  Their  characteristics  and  their  relations  to  the  hydro- 
carbons will  be  dwelt  upon,  as  well  as  their  relations  to  each 
other.  Thus  by  a  comparatively  close  study  of  two  hydro- 
carbons and  their  derivatives,  we  may  acquire  a  knowledge  of 
the  principal  classes  of  the  compounds  of  carbon.  After  these 
typical  derivatives  have  been  discussed,  the  entire  series  of 
hydrocarbons  will  be  taken  up  briefly,  only  such  facts  being 


RETROSPECT  107 

dealt  with  at  all  fully  as  are  not  illustrated  by  the  first  two 
members." 

In  accordance  with  the  plan  thus  sketched  we  have  thus  far 
studied  the  principal  derivatives  of  the  two  hydrocarbons, 
methane  and  ethane,  so  far  as  these  derivatives  represent  dis- 
tinct classes  of  compounds.  These  derivatives  were  classified 
first  into  (1)  those  containing  halogens ;  (2)  those  containing 
oxygen ;  (3)  those  containing  sulphur ;  and  (4)  those  contain- 
ing nitrogen.  On  examining  each  of  these  classes  more  closely, 
we  found  that  the  halogen  derivatives,  such  as  chlor-m ethane, 
brom-ethane,  etc.,  bear  very  simple  relations  to  each  other. 
We  found  that  under  the  head  of  oxygen  derivatives,  the  most 
important  and  most  distinctly  characteristic  derivatives  of 
hydrocarbons  are  met  with ;  as,  the  alcohols,  ethers,  aldehydes, 
acids,  ethereal  salts,  and  Jcetones.  The  sulphur  derivatives, 
some  of  which  closely  resemble  the  oxygen  derivatives,  include 
the  sulphur  alcohols  or  mercaptans,  sulphur  ethers,  and  sulphonic 
acids. 

On  beginning  the  consideration  of  the  nitrogen  derivatives 
we  found  it  desirable  first  to  take  up  certain  derivatives  con- 
taining the  cyanogen  group,  among  which  are  cyanogen,  hydro- 
cyanic acid,  cyanic  acid,  and  sulpho-cyanic  acid.  Many  interest- 
ing carbon  compounds  are  closely  related  to  these  fundamental 
compounds.  Such,  for  example,  are  the  cyanides  and  isocy- 
anides,  the  cyanates  and  isocyanates,  the  sulpho-cyanates  and 
iso-sulpho-cyanates  or  mustard-oils.  Following  the  compounds 
related  to  cyanogen,  we  took  up  the  interesting  compounds 
which  are  related  to  ammonia,  'the  substituted  ammonias  or 
amines.  Then  came  the  nitro-derivatives ;  and,  finally,  the 
compounds  of  the  hydrocarbon  residues  or  radicals  with  metals. 

It  is  of  the  greatest  importance  that  the  student  should 
master  the  preceding  portion  of  this  book.  If  he  studies  care- 
fully the  reactions  that  have  been  treated  of,  which  are  state- 
ments in  chemical  language  that  tell  us  the  conduct  of  the 
various  classes  of  derivatives,  and  if  he  performs  the  experi- 


108          DERIVATIVES    OF   METHANE   AND   ETHANE 

ments  that  have  been  described,  he  will  have  a  fair  general 
knowledge  of  the  kinds  of  relations  that  are  met  with  in  con- 
nection with  the  compounds  of  carbon  through  the  whole  field. 
As  stated  in  the  Introduction :  "  If  we  know  what  derivatives 
one  hydrocarbon  can  yield,  we  know  what  derivatives  we  may 
expect  to  find  in  the  case  of  every  other  hydrocarbon." 

The  more  the  student  practises  the  use  of  the  equations  thus 
far  given,  the  better  he  will  be  prepared  to  follow  the  remain- 
ing portions  of  the  book.  Indeed,  it  may  be  said  that,  if  he 
thoroughly  understands  what  has  gone  before,  what  follows  will 
appear  extremely  simple.  Whereas,  if  he  has  failed  at  any 
point  to  catch  the  exact  meaning,  if  he  has  failed  to  see  the 
connection,  he  had  better  go  back  and  faithfully  review,  or  he 
will  soon  find  his  mind  hopelessly  muddled,  and  relations  which 
are  as  clear  as  day  will  be  concealed  from  him. 

An  excellent  practice  is  to  trace  connections  between  the 
different  classes  of  compounds,  and  show  how  to  pass  from  one 
to  the  other.  Thus,  for  example,  (1)  show  by  what  reactions  it 
is  possible  to  pass  from  marsh  gas  to  acetic  acid.  (2)  How 
can  we  pass  from  ordinary  alcohol  to  ethylidene  chloride, 
CH3.CHC12?  (3)  What  reactions  enable  us  to  make  methyl- 
amine  from  its  elements  ?  (4)  How  can  acetone  be  made 
from  methyl-amine  ?  (5)  What  reactions  are  necessary  in 
order  to  make  ordinary  ether  from  ethyl-amine  ?  etc.,  etc. 
It  is  well  in  this  sort  of  practice  to  select  what  appear  to  be  the 
least  closely-related  compounds,  and  to  show  then  how  we  can 
pass  from  one  to  the  other.  Be  sure  to  select  representatives 
of  all  the  classes  hitherto  mentioned,  and  to  bring  in  all  the 
important  reactions. 


CHAPTER   VIII 

THE    HYDROCARBONS  OF   THE    MARSH-GAS    SERIES,  OR 
PARAFFINS 

THE  existence  of  the  homologous  series  of  hydrocarbons 
beginning  with  methane  and  ethane  was  mentioned  before  its 
first  two  members  were  discussed.  A  general  idea  of  the 
extent  of  the  series,  and  of  the  names  used  to  designate  the 
members,  may  be  gained  from  the  following  table :  — 

MARSH-GAS  HYDROCARBONS 
PARAFFINS.  — HYDROCARBONS,  CnH2n+2 

Boiling-point 


.  .  gas 

.  .  1° 

.  .  37° 

.  .  69° 

.  .  98° 

.  .  125° 

.  .  150° 

.  .  214° 

.  .  287° 

The  explanation  of  the  remarkable  relation  in  composition 
existing  between  these  members,  a  relation  to  which  the  name 
homology  is  given,  has  already  been  referred  to  (p.  23).  The 
number  of  hydrogen  atoms  contained  in  a  member  of  this  series 

109 


Methane      .     .     . 

.    CH4 

Ethane    .... 

.     C2H6 

Propane      .     .     . 

.     C3H8 

Butane    (normal) 

.    C4H10 

Pentane         "      . 

•     C5H!2 

Hexane         " 

.     C6H14 

Heptane        " 

.     C7H16 

Octane           " 

.     C8H18 

Nonane         " 

C*  TT 

•     v^grx^ 

Dodecane      " 

.     C12H26 

Hexadecane  " 

C16Ho4 

110        HYDROCARBONS   OF   THE  MARSH-GAS   SERIES 

bears  a  constant  relation  to  the  number  of  carbon  atoms,  as 
expressed  in  the  general  formula  CnH2n  +  2.  On  examining  the 
column  headed  "  Boiling-point "  it  will  be  seen  that,  as  we  pass 
upward  in  the  series,  the  boiling-point  becomes  higher  and 
higher.  The  first  three  members  are  gases  at  ordinary  tem- 
peratures, while  the  last  boils  at  287°.  The  elevation  in  the 
boiling-point  is  to  some  extent  regular,  as  will  be  observed. 
The  difference  between  butane,  C4H10,  and  pentaue,  C5H12,  is 
37  —  1  =  36° ;  that  between  pentane  and  the  next  member  is 
69  -  37  =  32° ;  between  hexane  and  heptane  it  is  98  -  69  =  29° ; 
between  heptane  and  octane,  125  —  98  =  27° ;  and,  finally, 
between  octane  and  nonane  the  difference  is  150  —  125  =  25°. 
Thus  it  will  be  seen  that  the  elevation  in  boiling-point  caused 
by  the  addition  of  CH2  decreases  as  we  pass  upward  in  the 
series.  Other  relations  have  been  pointed  out,  but  it  would 
be  premature  to  discuss  them  here. 

The  chief  natural  source  of  the  paraffins  is  petroleum ;  but 
although  this  substance,  which  occurs  in  such  enormous  quanti- 
ties in  nature,  undoubtedly  contains  a  number  of  the  members 
of  the  paraffin  series,  it  is  an  extremely  difficult  matter  to 
isolate  them  from  the  mixture.  Prolonged  fractional  distilla- 
tion is  not  sufficient  for  the  purpose.  If,  however,  some  of  the 
purest  products  that  can  thus  be  obtained  are  treated  with 
concentrated  sulphuric  acid,  and  afterwards  with  concentrated 
nitric  acid,  and  then  washed  and  redistilled,  they  can  be 
obtained  in  pure  condition. 

Petroleum. — Petroleum  occurs  in  enormous  quantities  in 
several  places.  Among  the  most  important  localities  are 
Pennsylvania,  Ohio,  California,  Texas,  the  Crimea,  the  Cau- 
casus, Persia,  Burmah,  China,  Mexico,  etc.  In  some  places 
it  issues  constantly  from  the  earth.  Usually  it  is  necessary 
to  bore  for  it.  When  one  of  the  cavities  in  which  it  is  con- 
tained is  punctured,  the  oil  is  forced  out  of  a  pipe  inserted 
into  the  opening  in  a  jet,  in  consequence  of  the  pressure 


PETROLEUM  111 

exerted  upon  its  surface.  As  first  obtained,  it  is  usually  a 
dark,  yellowish-green  liquid,  with,  an  unpleasant  odor.  It 
varies  in  appearance  according  to  the  place  where  it  is  found. 
American  petroleum  contains  the  lowest  members  of  the 
paraffin  series;  and  when  the  oil  is  exposed  to  the  air  the 
gases  are  given  off. 

Refining  of  petroleum.  To  render  petroleum  fit  for  use  in 
lamps,  it  is  necessary  that  the  volatile  portions  should  be 
removed,  as  they  form  explosive  mixtures  with  air,  just  as 
marsh  gas  does.  It  is  also  necessary  to  remove  the  higher 
boiling  portions,  because  they  are  semi-solid,  and  would  clog 
the  wicks  of  the  lamps.  The  crude  oil  is  therefore  subjected  to 
distillation,  and  only  those  parts  which  have  a  certain  specific 
gravity  or  boil  between  certain  points  are  used  for  illuminating 
purposes,  under  the  name  of  kerosene.  Besides  being  distilled, 
the  oil  must  further  be  treated  with  concentrated  sulphuric 
acid,  which  removes  a  number  of  undesirable  substances,  and 
afterwards  with  an  alkali,  and  then  with  water.  All  these 
processes  taken  together  constitute  what  is  called  the  refining 
of  petroleum.  In  the  distillation,  the  lighter  products  are 
usually  divided  into  several  parts,  according  to  the  specific 
gravity  or  boiling-point.  Thus  we  have  the  products  cymogene, 
rhigolene,  gasoline,  naphtha,  and  benzine,  all  of  which  are 
lighter  than  kerosene.  It  must  be  distinctly  understood  that 
the  substances  here  mentioned  are  not  pure  chemical  indi- 
viduals. The  names  are  commercial  names,  each  of  which 
applies  to  a  complex  mixture  of  hydrocarbons.  From  the 
heavier  products,  that  is,  those  that  boil  at  higher  tempera- 
tures than  the  highest  limit  for  kerosene,  paraffin,  which  is  a 
mixture  of  the  highest  members  of  this  series,  is  made. 

Owing  to  the  danger  attendant  upon  the  use  of  improperly 
refined  petroleum,  laws  have  been  enacted  relating  to  the 
properties  that  the  kerosene  exposed  for  sale  must  have. 
These  laws,  which  differ  somewhat  in  different  countries  and 
different  parts  of  the  same  country,  relate  mostly  to  what  is 


112        HYDROCARBONS   OF   THE   MARSH-GAS   SERIES 

called  the  flashing-point.  This  is  the  temperature  to  which  the 
oil  must  be  heated  before  it  takes  fire  when  a  flame  is  applied 
to  it.  The  legal  flashing-point  in  many  parts  of  the  United 
States  is  44°.  A  simple  and  accurate  instrument  for  deter- 
mining the  flashing-point  is  here  described :  The  cylinder  A 
is  at  least  2.5cm  in  diameter,  and  at  least  16cm  long.  Just 
within  the  cork  the  bent  tube  contracts  to 
a  small  orifice.  At  d  it  is  connected  with 
a  hand-bellows  or  a  gas-holder;  and  the 
flow  of  air  is  controlled  by  a  pinch-cock. 
The  cylinder  is  filled  with  oil  to  a  point 
such  that,  when  the  air  is  running,  the 
surface  of  the  foam  is  about  5cm  from  the 
top;  and  it  is  then  put  in  a  beaker  of 
water  to  the  level  of  the  oil.  Air  is  now 
passed  through  dc&,  and  e  so  adjusted  that 
Fig.  9.  about  0.5cm  foam  is  kept  on  the  surface  of 

the  oil.  The  water  in  the  beaker  is  now  gently  heated,  and,  from 
degree  to  degree,  the  test  is  made  by  bringing  a  small  flame  for 
an  instant  to  the  mouth  of  A.  At  the  flashing-point  the  vapor 
ignites,  and  the  bluish  flame  runs  down  to  the  surface  of  the  oil. 

Experiment  31.  Make  an  apparatus  like  the  above,  and  determine 
the  flashing-points  of  two  or  three  specimens  of  kerosene  that  may  be 
available. 

Synthesis  of  the  paraffins. — Although  the  paraffins  occur 
in  nature,  and  a  few  of  them  can  be  obtained  in  pure  condition 
from  natural  sources,  we  are  dependent  upon  synthetical  oper- 
ations performed  in  the  laboratory  for  our  knowledge  of  the 
series  and  the  relations  existing  between  them. 

We  have  already  seen  how  ethane  can  be  prepared  from 
methane  by  treating  methyl  iodide  with  zinc  or  sodium,  as 
represented  in  this  equation :  — 

CH3I  +  CH3I  +  2  Na  =  C2H6  +  2  NaJ. 


SYNTHESIS   OF  THE  PARAFFINS  113 

This  method  has  been  extensively  used  in  the  building  up  of 
higher  members  of  the  series.  Thus  from  ethane  we  can  make 
ethyl  iodide,  and  by  treating  this  with  sodium  get  butane, 
C4H10  :  — 

C2H5I  +  C2H5I  +  2  Na  =  C4H10  +  2  Nal. 

But  we  can  get  the  intermediate  member,  propane,  C3H8,  by 
mixing  methyl  iodide  and  ethyl  iodide  and  treating  the  mixture 
with  sodium  :  — 

CH3I  +  C2H5I  +  2  Na  =  CH3.C2H5  +  2  Nal. 

By  applying  this  method,  it  is  plain  that  a  large  number  of  the 
members  of  the  paraffin  series  might  be  made. 

Another  method  consists  in  treating  the  zinc  compounds  of 
the  radicals,  like  zinc  ethyl,  Zn(C2H5)2,  with  the  iodides  of  rad- 
icals. Thus  zinc  methyl  and  methyl  iodide  give  ethane;  zinc 
ethyl  and  ethyl  iodide  give  butane,  etc.  :  — 

Zn(CH3)2  +  2  CH3I  =  2  C2H6  +  ZnI2  ; 
Zn(C2H5)2  +  2  C2H5I  =  2  C4H10  +  ZnI2. 

Paraffins  can  be  made  by  replacing  the  halogen  in  a  substitu- 
tion-product by  hydrogen.  This  can  be  effected  by  nascent 
hydrogen  or  by  hydriodic  acid:  — 


As  these  halogen  substitution-products  can  easily  be  made 
from  tho  alcohols,  it  follows  that  the  hydrocarbons  can  be  made 
from  the  corresponding  alcohols. 

The  Barbier-Grignard  reaction  may  also  be  used  for  the  pur- 
pose of  passing  from  a  mono-halogen  substitution-product  of  a 
paraffin  to  the  paraffin  itself  (see  p.  106). 

Finally,  the  paraffins  can  be  made  by  heating  the  acids  of 
the  formic  acid  series  with  an  alkali.  This  has  been  illus- 
trated by  the  preparation  of  marsh  gas  from  acetic  acid  by  heat- 


114         HYDROCARBONS   OF    THE   MARSH-GAS   SERIES 

ing  with  lime  and  caustic  soda.     The  reaction  may  be  written 
thus  :  -  =  CH4  +  C03Na2. 


The  products  are  a  hydrocarbon  and  a  carbonate. 

Isomerism  among  the  paraffins.  —  It  has  already  been 
stated  that  the  evidence  is  strongly  in  favor  of  the  view  that 
'each  of  the  four  hydrogen  atoms  of  marsh  gas  bears  the  same 
relation  to  the  carbon,  arid  therefore  that,  as  regards  the 
nature  of  the  product,  it  makes  no  difference  which  hydrogen 
atom  is  replaced  by  a  given  atom  or  radical.  According  to  this, 
as  ethane  is  the  methyl  derivative  of  marsh  gas,  it  makes 
no  difference  which  of  the  hydrogen  atoms  of  marsh  gas  is 
replaced  by  the  methyl,  the  product  must  always  be  the 
same,  or  there  is  only  one  ethane  possible  according  to  the  theory, 
and  only  one  ethane  has  ever  been  discovered.  This  is  repre- 

H    H 

I       I 
sented  by  the  formula,  H  -  C  -  C  -  H,  or  H3C  -  CH3.    In  ethane, 

I      I 

H     H 

as  well  as  in  methane,  all  the  hydrogen  atoms  bear  the  same 
relation  to  the  molecule,  and  it  should  make  no  difference 
which  one  is  replaced  by  methyl.  But  propane  is  regarded  as 
derived  from  ethane  by  the  substitution  of  methyl  for  hydro- 
gen ;  and,  as  it  makes  no  difference  which  hydrogen  is  replaced, 
there  is  but  one  propane  possible.  Only  one  has  ever  been  dis- 
covered, and  this  must  be  represented  thus  :  — 

H     H     H 

I        I        I 

H-C-C-C-H,  or  CH3.CHo.CH3. 
I        I        I 
H     H     H 

Now,  continuing  the  substitution  of  methyl  for  hydrogen, 
it  appears  that  the  theory  indicates  the  possibility  of  the 
existence  of  two  compounds  of  the  formula  C4H10.  One  of 
these  should  be  obtained  by  substituting  methyl  for  one  of 


ISOMERISM    AMONG   THE   PARAFFINS  115 

the  three  hydrogens  of  either  methyl  group  of  propane.  It  is 
represented  by  the  formula  :  — 

H     H     H     H 

I        I        I        I 

H-C-C-C-C-H,  or  H3C.CH2.CH2.CH3. 
I        I        I        I 
H     H     H      H 

The  other  should  be  obtained  by  substituting  methyl  for  one 
of  the  two  hydrogens  of  the  group  CH2  contained  in  propane. 
This  would  give  a  hydrocarbon  of  the  formula  :  — 

H     H     H 

I        I        I 
H  -  C  -  C  -  C  -  H,  or  CH3  -  CH  -  CH3. 

Ill  I 

H     C      H  CH3 


The  theory  then  indicates  the  existence  of  two  butanes.  How 
about  the  facts  ?  Two,  and  only  two,  butanes  have  been  dis- 
covered. The  first,  which  occurs  in  American  petroleum,  has 
been  made  synthetically  by  treating  ethyl  iodide  with  zinc:  — 

2  CH3.CH2I  +  Zn  =  CH3.CH2.CH2.CH3  +  ZnI2. 

The  method  of  synthesis  clearly  shows  which  of  the  two  possi- 
ble isomerides  the  product  is.  It  is  known  as  normal  butane. 
It  is  a  gas  that  can  be  condensed  to  a  liquid  at  +  1°. 

The  second,  or  isobutane,  is  made  from  an  alcohol  which 
will  be  shown  to  have  the  structure  represented  by  the  formula 
CH3 

CH3  -  C  -  OH  (see  Tertiary  Butyl  Alcohol,  p.  125),  by  replacing 
I 

CH3 

the  hydroxyl  by  hydrogen.  It  is  a  gas  that  becomes  liquid 
at  -  17°. 

The  differences  between  the  two  butanes  show  themselves 
most  strikingly  in  their  derivatives. 


116        HYDROCARBONS   OF   THE   MARSH-GAS   SERIES 

Applying  the  same  method  of  reasoning  to  the  next  member 
of  the  series,  how  many  isomeric  varieties  of  pentane,  C5H12, 
does  the  theory  suggest  ?     The  question  resolves  itself  into  a 
determination  of  the  number  of  kinds  of  hydrogen  atoms  con- 
tained in  the  two  butanes,  or  the  number  of  relations  to  the 
molecule  represented  among  the  hydrogen  atoms  of  the  butanes. 
This  determination  can  be  made  best  by  examining  the  struc- 
tural formulas.     Take  first  normal  butane :  — 
H     H     H     H 
I        I        I        I 
H-C-C-C-C-H. 
I        I        I        I 
H     H     H     H 

In  this  there  are  plainly  two  different  relations  represented  j 
viz.,  that  of  each  of  the  six  hydrogens  in  the  two  methyl  groups, 
and  that  of  each  of  the  four  hydrogens  of  the  two  CH2  groups. 
The  two  possible  methyl  derivatives  of  a  hydrocarbon  of  this 
formula  are  therefore  to  be  represented  thus :  — 

H3C.CH2.CH2.CH2.CH3,  (1) 

and  H3C.CH2.CH<^3.  (2) 

L>tiB 
CH3 
I 

Now,   taking  isobutane,  HC  — CH3,  it  will  be  seen  that  it  con- 

I 

CH3 

sists  of  three  methyl  groups,  giving  nine  hydrogen  atoms  of  the 
same  kind,  and  one  CH  group,  the  hydrogen  of  which  bears  a 
different  relation  to  the  molecule  from  that  which  the  other 
nine  do.  There  are  therefore  two  possible  methyl  derivatives 
of  isobutane  which  must  be  represented  thus  :  — 
CH3  CH3 

I  I 

HC-CH2.CH3  (3),         and  H3C  -  C  -  CH3.  (4) 

I  I 

CH3  CH3 


PENTANES  117 

We  have,  therefore,  apparently  four  pentanes.  But  on  compar- 
ing formulas  (2)  and  (3),  it  will  be  seen  that,  though,  written 
a  little  differently,  they  really  represent  one  and  the  same 
compound.  Thus  the  number  of  pentanes,  the  existence  of 
which  is  indicated  by  the  theory,  is  three,  and  these  are  repre- 
sented by  formulas  (1),  (2),  and  (4).  They  are  all  known. 
The  first  is  called  normal  pentane,  the  second  iso-pentane, 
or  di-methyl-ethyl-methane,  and  the  third  tetra-methyl- 
methane. 

It  would  lead  too  far  to  discuss  all  the  methods  of  prep- 
aration and  the  properties  of  these  hydrocarbons.  It  will 
be  seen  that  the  methods  of  preparation  show  what  the 
structure  of  a  hydrocarbon  is.  Di-methyl-ethyl-methane,  for 
example,  is  made  from  an  alcohol  which  can  be  shown  to 
have  the  formula, 


CH.CH2.CH2OH, 


by  replacing  the  hydroxyl  by  hydrogen.     Hence  its  structure  is 
that  represented,  above  by  formulas  (2)  and  (3). 

Tetra-methyl-methane  is  made  by  starting  with  acetone. 
Acetone  has  been  shown  to  consist  of  carbonyl  in  combina- 
tion with  two  methyl  groups,  as  represented  in  the  formula 
CH3  —  CO  —  CH3.  It  has  also  been  shown  that,  by  treating 
acetone  with  phosphorus  pentachloride,  the  oxygen  is  replaced 
by  chlorine,  giving  a  compound  of  the  formula  CH3—  CC12—  CH3. 
Now,  by  treating  this  chloride  with  zinc-methyl,  the  chloride  is 

replaced  by  methyl  thus  :  — 

CH3 
I 

CH3  -  CC12  -  CH3  +  Zn(CH3)2  =  CH3  -  C  -  CH8  +  ZnCL, 

I 
CH3 

The  product  is  tetra-methyl-m  ethane,  and  this  synthesis 
shows  clearly  what  the  structure  of  the  product  is. 


118        HYDROCARBONS   OF   THE   MARSH-GAS    SERIES 

Hexanes.  —  The  student  will  now  be  prepared  to  apply  the 
theory  to  the  determination  of  the  number  of  hexanes  possible. 
He  will  find  that  there  are  five.  The  theory  is,  in  this  case  as 
in  the  preceding,  in  perfect  accordance  with  the  facts.  There 
are  five,  and  only  five,  hexanes  known.  Only  the  names  and 
formulas  of  these  will  be  given  here  :  — 

1.  Normal  hexane,  CH3.CH2.CH2.CH2.CH2.CH3. 

PTT 

2.  Iso-hexane,  CH3.CH2.CH2.CH<  ~/. 


3.  Methyl-di-ethyl-methane, 

TT  p 

4.  Tetra-methyl-ethane,     '^  >  HC  -  CH  < 

il3L- 

CH3 
I 

5.  Tri-methyl-ethyl-methane,  H3C  -  C  - 

I 
CH3 

Passing  upward,  we  find  that  nine  heptanes  are  possible 
according  to  the  theory,  while  but  Jive  have  thus  far  been  dis- 
covered ;  and  that,  while  theory  indicates  the  possibility  of  the 
discovery  of  eighteen  hydrocarbons  of  the  formula  08H18,  but 
Jive  are  known.  The  theoretical  number  of  isomeric  varieties 
of  the  highest  members  of  the  series  is  very  great,  but  our 
knowledge  in  regard  to  these  highest  members  is  quite  limited, 
and  it  is  impossible  to  say  whether  the  theory  will  ever  be 
confirmed  by  facts.  It  may  be  that  there  is  some  law  limiting 
the  number  of  complicated  hydrocarbons.  It  is,  however,  idle 
to  speculate  upon  the  subject.  It  is  well  for  us  to  keep  in 
mind  that  a  thorough  knowledge  of  a  few  of  the  simplest 
members  of  the  series  is  all  that  is  necessary  for  the 
present. 

On  examining  the  formulas  used  to  express  the  structure  of 


HEXANES  119 

the  hydrocarbons,  we  find  that  they  can  be  divided  into  three 
classes  :  — 

(1)  Those  in  which  there  is  no  carbon  atom  in  combination 
with  more  than  two  others  j  as,  — 

Propane     ....  CH3.CH2.CH3; 
Normal  butane   .     .  CH3.CH2.CH2.CH3; 
Normal  pentane.     .  CH3.CH2.CH2.CH2.CH3; 
and        Normal  hexane  .     .  CH3.CH2.CH2.CH2.CH2.CH3. 

(2)  Those  in  which   there  is  at  least   one  carbon  atom  in 
combination  with  three  others  ;  as,  — 


Isobutane  ....  CH3.CH< 

' 

Isopentane     .     .    .  CH3.CH2.CH 

Isohexane.     .     .     .  CH3.CH2.CH2.CH<^7; 

TT    p 

and         Tetra-methyl-ethane,  ^  >  CH  -  CH  < 

(3)  Those   in  which  there  is  at  least  one  carbon  atom  in 
combination  with  four  others  ;  as,  — 

CH3 

Tetra-methyl-) 


. 

,1  •       «    \jti»  —  O  —  v^-tlaj 

methane      )  , 

CH3 
CH3 

and         Tri-methyl-ethyl-  )  ^  _ 

methane  )  I 

CH3 

The  members  of  the  first  class  are  called  normal  paraffins; 
those  of  the  second  class,  iso-parafflns  ;  and  those  of  the  third 
class,  neo-parajfins. 


120        HYDROCARBONS    OF    THE   MARSH-GAS    SERIES 

Only  the  members  of  the  same  class  are  strictly  comparable 
with  one  another.  Thus  it  has  been  found  that  the  boiling- 
points  of  the  normal  hydrocarbons  •  bear  simple  relations  to 
one  another,  and  that  the  same  is  true  of  the  iso-paraffins  ; 
but,  on  comparing  the  boiling-points  and  other  physical  prop- 
erties of  normal  paraffins  with  those  of  the  iso-  or  neo-paraffins, 
no  such  simple  relations  are  observed. 

Regarding  the  names  of  the  paraffins,  the  simplest  nomen- 
clature in  use  is  that  according  to  which  the  hydrocarbons  are 
all  regarded  as  derivatives  of  methane.  Thus  we  get  the 

fC2H5 

H 
name  ethyl-methane  for  propane,  Cl  H       ;  tri-methyl-methane 

CH3  IH  CH3 


8;   tetra-methyl-m  ethane,  c     ;3  etc. 

CH8  LH3 

H  LCH8 


CHAPTER   IX 

OXYGEN  DERIVATIVES    OF   THE    HIGHER  MEMBERS  OF 
THE   PARAFFIN  SERIES 

WE  are  now  to  take  up  the  derivatives  of  the  higher  mem- 
bers of  the  paraffin  series,  just  as  we  took  up  the  derivatives  of 
methane  and  ethane.  Not  much  need  be  said  in  regard  to  the 
halogen  derivatives.  A  few  of  them  will  be  mentioned  in  con- 
nection with  the  corresponding  alcohols.  The  chief  substances 
that  will  require  attention  are  the  alcohols  and  acids. 

1.   ALCOHOLS 

Normal  propyl  alcohol,  propanol,  C3H7OH.  —  When 
sugar  undergoes  fermentation,  a  little  propyl  alcohol  is  always 
formed,  and  is  contained  in  the  "fusel  oil."  From  this  it  can 
be  separated  by  treating  those  portions  which  boil  between 
85  °  and  110  °  with  phosphorus  and  bromine.  The  bromides  of 
the  alcohols  present  are  thus  formed  (what  is  the  reaction?), 
and  these  are  separated  by  fractional  distillation.  The  bro- 
mide corresponding  to  propyl  alcohol  is  then  converted  into 
the  alcohol  (how  can  this  be  done?). 

It  is  a  colorless  liquid  with  a  pleasant  odor.  It  boils  at  97° 
(compare  with  the  boiling-points  of  methyl  and  ethyl  alcohol). 
It  conducts  itself  almost  exactly  like  the  first  two  members  of 
the  series.  By  oxidation  it  is  converted  into  an  aldehyde, 
C3H60,  and  an  acid,  C3H602,  which  bear  to  it  the  same  relations 
that  acetic  aldehyde  and  acetic  acid  bear  to  ethyl  alcohol. 

Secondary  propyl   or    isopropyl    alcohol,    C3H;OH. — 

The  reasons  for  regarding  the  alcohols  as  hydroxyl  derivatives 

121 


122  DERIVATIVES   OF   THE  PARAFFINS 

of  the  hydrocarbons  have  been  given  pretty  fully.  As  the  six 
hydrogen  atoms  of  ethane  are  all  of  the  same  kind,  but  one 
ethyl  alcohol  appears  to  be  possible,  and  only  one  is  known. 
But  just  as  there  are  two  butanes  or  methyl  derivatives  of  pro- 
pane, so  there  are  two  hydroxyl  derivatives  of  propane ;  or,  in 
other  words,  two  propyl  alcohols.  The  first  is  the  one  obtained 
from  "  fusel  oil,"  the  other  is  the  one  called  secondary  propyl 
alcohol.  This  has  already  been  referred  to  under  the  head  of 
Acetone  (see  p.  73),  where  it  was  stated  that  acetone  is  con- 
verted into  secondary  propyl  alcohol  by  nascent  hydrogen. 
We  are,  in  fact,  dependent  upon  this  method  for  the  prepara- 
tion of  the  alcohol. 

It  is,  like  ordinary  propyl  alcohol,  a  colorless  liquid.  It 
boils  at  81°.  While  all  its  reactions  show  that  it  is  a  hydrox- 
ide, under  the  influence  of  oxidizing  agents  it  conducts  itself 
quite  differently  from  the  alcohols  thus  far  considered.  It  is 
converted  first  into  acetone,  C3H60,  which  is  isomeric  with  the 
aldehyde  obtained  from  ordinary  propyl  alcohol;  by  further 
oxidation,  it  however  does  not  yield  an  acid  of  the  formula 
C3H602,  as  we  should  expect  it  to,  but  breaks  down,  yielding 
two  simpler  acids;  viz.,  formic  acid,  CH202,  and  acetic  acid, 
C2H402. 

Secondary  alcohols.  —  Secondary  propyl  alcohol  is  the 
simplest  representative  of  a  class  of  alcohols  known  as 
secondary  alcohols.  They  are  made  by  treating  the  ketones 
with  nascent  hydrogen,  and  are  easily  distinguished  from  other 
alcohols  by  their  conduct  toward  oxidizing  agents.  They 
yield  acetones  containing  the  same  number  of  carbon  atoms, 
and  then  break  down,  yielding  acids  containing  a  smaller  num- 
ber of  carbon  atoms. 

Is  there  anything  in  the  structure  of  these  secondary  alcohols 
to  suggest  an  explanation  of  their  conduct  ?  Secondary  propyl 
alcohol  is  made  from  acetone  by  treating  this  with  nascent  hy- 
drogen. Acetone  contains  two  methyl  groups  and  carbonyl,  as 


SECONDARY   ALCOHOLS  123 

represented  by  the  formula  CH3  —  CO  —  CH3.  The  simplest 
change  that  can  take  place  in  this  compound  under  the  influence 
of  hydrogen  is  that  represented  in  the  following  equation :  — 

CH3  -  CO  -  CH3  +  H2  =  CH3  -  CH.OH  -  CH3. 

The  very  close  connection  existing  between  acetone  and  second- 
ary propyl  alcohol,  and  the  fact  that  there  are  two  methyl 
groups  in  acetone,  make  it  appear  probable  that  there  are  also 
two  methyl  groups  in  secondary  propyl  alcohol,  as  represented 
in  the  above  equation.  On  the  other  hand,  the  easy  transfor- 
mation of  primary  propyl  alcohol  into  propionic  acid,  which  can 
be  shown  to  contain  ethyl,  shows  that  in  the  alcohol  ethyl  is 
present.  Therefore,  we  may  conclude  that  the  difference 
between  primary  and  secondary  propyl  alcohol  is  that  the 
former  is  an  ethyl  derivative  and  the  latter  a  di-methyl  deriva- 
tive of  methyl  alcohol,  as  represented  by  the  formulas :  — 


r  CH2-CH8 

fCH, 

c   H 

r    CH8. 

J    H 

C    H 

I  OH 

I  OH 

Ethyl-methyl  alcohol  or 
ordinary  propyl 
alcohol 

Dimethyl-methyl  alco- 
hol or  secondary 
propyl  alcohol 

Primary  propyl  alcohol  is  ^fiethyl  alcohol  in  which  one  hydrogen 
is  replaced  by  a  radical,  while  secondary  propyl  alcohol  is 
methyl  alcohol  in  which  two  hydrogens  are  replaced  by  radicals. 
An  examination  of  all  secondary  alcohols  known  shows  that 
the  above  statement  can  be  made  in  regard  to  all  of  them. 
They  must  be  regarded  as  derived  from  methyl  alcohol  by  the 
substitution  of  two  radicals  for  two  hydrogen  atoms.  The  alco- 
hols of  the  first  class,  like  methyl,  ethyl,  and  ordinary  propyl 
alcohols,  which  are  derived  from  methyl  alcohol  by  the  substitu- 
tion of  one  radical  for  one  hydrogen,  are  called  primary  alcohols. 
Another  way  of  stating  the  difference  between  primary  and 
secondary  alcohols  is  this :  Primary  alcohols  contain  the  group 


124  DERIVATIVES   OF   THE   PARAFFINS 

CH2OH ;  secondary  alcohols  contain  the  group  CHOH.  These 
statements  necessarily  follow  from  the  first  ones. 

A  primary  alcohol,  when  oxidized,  yields  an  aldehyde  and 
then  an  acid  containing  the  same  number  of  carbon  atoms  as 
the  alcohol. 

A  secondary  alcohol,  when  oxidized,  yields  a  ketone  and 
then  an  acid  or  acids  containing  a  smaller  number  of  carbon 
atoms. 

Recalling  what  was  said  regarding  the  nature  of  the  changes 
involved  in  passing  from  an  alcohol  to  the  corresponding  alde- 
hyde and  acid,  it  will  be  seen  that  the  formation  of  the  acid  is 
impossible  in  the  case  of  a  secondary  alcohol.  In  the  case  of 
a  primary  alcohol,  we  have :  — 

K 


fK 

ojs 

lo 


Aldehyde  Acid 

In  the  case  of  the  secondary  alcohol,  we  have :  — 
E  fT> 

c  R  ell 

°     H  P>tff 


Secondary  alcohol  Ketone 

Further  introduction  of  oxygen  cannot  take  place  without  a 
breaking  down  of  the  compound.  It  will  be  seen  that  the 
formulas  used  to  express  the  structure  of  the  compounds  are 
in  close  accordance  with  the  facts. 


Butyl  alcohols,  C^.OH.  —  Theoretically,  there  are  two 
possible  hydroxyl  derivatives  of  each  of  the  two  butanes, 
making  four  butyl  alcohols  in  all.  They  are  all  known.  Two 
are  primary  alcohols. 


BUTYL   ALCOHOLS  125 

1.  Normal  butyl  alcohol,  CH3.CH2.CH2.CH2OH. 

pTT 

2.  Isobutyl  alcohol,  Qjj3>CH.CH2OH. 

The  third  is  a  derivative  of  normal  butane,  and  is  a  secondary 
alcohol. 

OTT 

3.  Secondary  butyl  alcohol,  CH3.CH2.CH<;;^:  •     This 


alcohol  is  prepared  by  treating  ethyl-methyl  ketone  with  nas- 
cent hydrogen  :  — 

CH3.CH2-  CO  -  CH3  +  H2  =  CH3.CH2.CH  < 


(Compare  this  with  the  reaction  for  making  secondary  propyl 
alcohol.)  CH3 

4.  Tertiary  butyl  alcohol,  CH3  -  C  -  OH.    The  fourth  butyl 

I 

CH3 

alcohol  has  properties  that  distinguish  it  from  the  primary 
and  secondary  alcohols.  When  oxidized  it  yields  neither  an 
aldehyde  nor  an  acetone,  but  breaks  down  at  once,  yielding 
acids  containing  a  smaller  number  of  carbon  atoms.  Assum- 
ing that  every  primary  alcohol  contains  the  group  CH2OH, 
and  that  every  secondary  alcohol  contains  the  group  CHOH, 
it  follows  that  the  two  primary  butyl  alcohols  and  secondary 
butyl  alcohol  must  have  the  formulas  above  assigned  to  them  ; 
and  it  follows  further,  that  the  fourth  butyl  alcohol  must  have 
CH3 

the  formula  CH3  —  C  —  OH,  as  this  represents  the  only  other 
I 
CH3 

arrangement  of  the  constituents  possible,  according  to  our 
theory.  This  formula  represents  a  condition  which  does  not 
exist  in  either  the  primary  or  secondary  alcohols.  It  is 
methyl  alcohol  in  which  all  the  hydrogen  atoms,  except  that 
of  the  hydroxyl,  are  replaced  by  methyl  groups.  It  con- 
tains the  group  C—  (OH).  Such  an  alcohol  is  known  as  a 


126  DERIVATIVES    OF    THE   PARAFFINS 

tertiary  alcohol,  and  the  one  under  consideration  is  called  ter- 
tiary butyl  alcohol.  It  is  the  simplest  derivative  of  a  class  of 
which  but  few  members  are  known. 

Tertiary  butyl  alcohol  is  made  by  treating  acetone  with 
methyl  magnesium  bromide,  CH3MgBr  (Barbier-Grignard  re- 
agent), and  then  treating  the  product  with  water :  — 

fCH3 

(CH8)2CO  +  CH3MgBr  =  C  J  ^3  J 

CH3 

lOMgBr 

|CH3  rCH3 

CH3  I  CH3 

CH3+H2°  =C     CH3 

OMgBr  [OH 

By  using  other  ketones  and  magnesium  compounds  contain- 
ing other  radicals,  other  tertiary  alcohols  can  be  obtained. 

Characteristics  of  the  three  Classes  of  Alcohols.  To  recapitu- 
late, the  hydroxyl  derivatives  of  the  hydrocarbons  can  be 
divided  into  three  classes,  according  to  their  conduct  towards 
oxidizing  agents. 

To  what  was  said  above  regarding  the  conduct  of  primary 
and  secondary  alcohols  we  may  now  add :  Tertiary  alcohols 
yield  neither  aldehydes  nor  acetones  containing  the  same 
lumber  of  carbon  atoms,  but  generally  break  down,  yielding 
simpler  acids. 

The  formulas  representing  the  three  classes  of  alcohols  are :  — 


and 


Pentyl  alcohols,  C5HU.OH. — Eight  of  these  are  possible, 
and  all  are  known.  Only  the  two  amyl  alcohols  need  be  taken 
up  here. 


AMYL   ALCOHOLS  127 

Inactive    amyl    alcohol,        ?E3  >  CH  -  CH2  -  CH2OH.  — 


This  alcohol,  together  with  at  least  one  other  of  the  same  com- 
position, forms  the  chief  part  of  "  fusel  oil."  By  fractional 
distillation  of  this,  ordinary  amyl  alcohol  is  obtained,  as  a 
colorless  liquid,  having  a  penetrating  odor,  and  boiling  at  131° 
to  132°.  This  can  be  separated  by  other  methods  into  two 
isomeric  alcohols,  one  of  which  is  inactive  amyl  alcohol  and 
the  other  active  amyl  alcohol.  The  names  refer  to  the  behav- 
ior of  the  substances  towards  polarized  light,  the  former 
having  no  action  upon  it,  the  latter  turning  the  plane  of  polar- 
ization to  the  left. 

When  treated  with  oxidizing  agents  inactive  amyl  alcohol 
yields  an  acid  containing  the  same  number  of  carbon  atoms, 
and  is,  therefore,  a  primary  alcohol.  The  acfd  has  been  made 
by  simple  reactions  which  show  that  it  must  be  represented  by 

the  formula  ^H3>CH.CH2.C02H.     Therefore,  the  alcohol  has 


the  structure  represented  by  the  formula  CH3>CH.CH2.CH2OH. 
Active  amyl  alcohol,  CH3.CH2.CH<^'       .  —  This,  as 


has  been  stated,  is  obtained,  together  with  the  inactive  alcohol, 
from  fusel  oil.     It  is  a  primary  alcohol  as  represented. 

A  list  of  some  of  the  more  important  remaining  members  of 
the  series  is  given  below.  In  naming  the  alcohols,  it  is  best 
to  refer  them  to  methyl  alcohol,  just  as  the  hydrocarbons  are 
referred  to  marsh  gas.  Calling  methyl  alcohol  carUnol,  we  get 
such  names  as  methyl-carbinol,  di-ethyl-carbinol,  etc.,  which 
convey  at  once  an  accurate  idea  concerning  the  structure  of 
the  substances.  A  few  illustrations  will  suffice.  Take  the 
alcohols  considered  above  :  — 

3          ft 

Ethyl  alcohol  is  methyl-carbinol,  C  \  „    j 

xi  - 

OH 


128 


DERIVATIVES    OF    THE   PARAFFINS 


Primary  propyl  alcohol  is  ethyl-carbinol,       C 


CH2CHa 
H 

H    5 
OH 

OH, 


Secondary  propyl  alcohol  is  di-methylr  I  CH3 

carUnol,  °  ]  H     > 

OH 

CH3 

/•ITT 

Tertiary  butyl  alcohol  is  tri-methyl-carbinol,  G  •{  ^r,-3  > 

OH 


Inactive  amyl  alcohol  is  isobutyl-carbinol,     G 


H 
H 

OH,  etc.,  etc., 


a  name  given  to  it  on  account  of  the  presence  in  it  of  the 
isobutyl  group  CH2.CH<™3. 


The  following  table  will  give  an  imperfect  idea  of  the  extent 
to  which  the  series  of  alcohols  derived  from  the  paraffins  has 
been  investigated.  There  are  fourteen  hexyl  alcohols  and 
thirteen  heptyl  alcohols  known. 

Cetyl  alcohol,  CjeHgg.OH,  is  the  chief  constituent  of  sper- 
maceti. 

Ceryl  alcohol,  C^H^On,  is  found  in  Chinese  wax. 

Myncyl  alcohol,  C^H^-OH,  occurs  in  beeswax  and  in  Car- 
nauba  wax.  . 

Of  most  of  the  higher  members  but  one  variety  is  known. 
They  are  not  important,  except  in  so  far  as  they  indicate  the 
possibility  of  the  discovery  of  other  alcohols. 


ALDEHYDES  129 

ALCOHOLS    OF    THE    METHYL    ALCOHOL    SERIES 

SERIES  CJl^.OH. 

Methyl  alcohol       CH3.OH 

Ethyl  « C2H5.OH 

Propyl  «             C3H7.OH 

Butyl  «            C4H9.OH 

Pentyl  «  .........  C5HU.OH 

Hexyl  «            C6H13.OH 

Heptyl  «            C7H15.OH 

Octyl  "            .  C8H17.OH 

Nonyl  «             C9H19.OH 

Cetyl  «             deHa.OH 

Ceryl  « C26H53.OH 

Myricyl  «            CgoH^.OH 

2.   ALDEHYDES 

In  general,  it  follows  from  what  has  been  said  concerning 
the  properties  of  primary  alcohols,  that  there  should  be  an 
aldehyde  corresponding  to  every  primary  alcohol.  Many  of 
these  have  been  prepared.  They  resemble  ordinary  acetic 
aldehyde  so  closely  that  it  is  unnecessary  to  take  them  up 
individually.  If  the  structure  of  the  alcohol  from  which  an 
aldehyde  is  formed  by  oxidation  is  known,  the  structure  of  the 
aldehyde  is  also  known. 

Besides  the  one  method  for  the  preparation  of  aldehydes 
that  has  been  mentioned,  viz.,  the  oxidation  of  primary 
alcohols,  there  is  one  other  that  should  be  specially  noted. 
It  consists  in  distilling  a  mixture  of  a  formate  and  a  salt  of 
some  other  acid.  Thus,  when  a  mixture  of  an  acetate  and  a 
formate  is  distilled,  acetic  aldehyde  is  formed  as  represented 
by  the  equation :  — 

W '  PHAM  =  CH" '  C°H 
H  .  COOM  Aldehyde 


130  DERIVATIVES   OF   THE   PARAFFINS 

This  method  has  been  used  to  a  considerable  extent  in  making 
the  higher  members  of  the  series. 

Experiment  32.  Mix  about  equal  weights  of  dry  calcium  formate 
and  dry  calcium  acetate.  Distil  from  a  small  flask.  Collect  some  of  the 
distillate  in  water,  and  determine  whether  aldehyde  is  formed. 

3.    ACIDS 

Formic  and  acetic  acids  are  the  first  two   members  of  an 
homologous  series  of  similar  acids,  generally  called  the  fatty 
acids  because  several  of  them  occur  in  large  quantities  in  the 
natural  fats.     The  names  and  formulas  of  some  of  the  principal 
members  are  given  in  the  following  table.     The  reasons  for 
representing  the  acids  as  compounds  containing  the  carboxyl 
group,  C02H,  have  been  given,   and  need  not  here  be  re- 
stated :  — 

FATTY  ACIDS 

SERIES  CnH2n+1  .  C02H,  or  C^H^O, 
Formic    acid       .........  H.C02H 

Acetic       «         .........       CH3.C02H 

Propionic"          .........       C2H5.C02H 

Butyric     "          .........       C3H7.C02H 

Valeric      "          .........      C4H9.C02H 

Caproic  or 
,T        .         .  , 
Hexoic  acids 


1 
\ 
J 


(Enanthylic  or 
TT     ,   .        .  , 
Heptoic  acids 

°af7lic°r        }     ........     C?H1S.C02H 

Octoic  acids       J 

Pelargonicor    |      .......   I  C8H17.C02H 

Nonoic  acids      J 

Capric  acid    ..........  C9H]9.C02H 

Laurie     «       ..........  CuH23.CO.jH 


PROPIONIC    ACID  131 

Myristic  acid .    .    .  dgH^.CO^ 

Palmitic     «  C15H31.C02H 

Margaric     "  deH^.COaH 

Stearic        «  C^H 

Arachidic  «  C^H 

Behenic      «  C^H^CO,!! 

Hyenic       " C24H49.C02H 

Cerotic        "  C^H^CO,,!! 

Melissic      "  C^H^.COaH 

Although,  as  will  be  seen,  a  large  number  of  fatty  acids  are 
known,  most  of  those  included  in  the  list  are  at  present  merely 
curiosities,  and  need  not  be  specially  studied.  Not  more  than 
six  in  addition  to  formic  and  acetic  acids  will  require  attention. 

Propionic  acid,  propanic  acid,  C3H6O2(C2H5.  CO£I).— 

Propionic  acid  is  formed  in  small  quantity  (1)  by  the  distil- 
lation of  wood;  (2)  by  the  fermentation  of  various  organic 
bodies,  particularly  calcium  lactate~and~^ai'tratej^  (3)  by  treat- 
ing  ethyl  cyanide  (propio-nitrile)  with  caustic  potash :  — 

C2H5 .  ON  +  KOH  +  H20  =  C2H5 .  C02K  -f  NH3 ; 

and  (4)  by  oxidizing  normal  propyl  alcohol.  This  last  method 
is  used  on  the  large  scale. 

Other  methods  for  preparing  it  are  the  following:  — 

(1)  By  reducing  lactic  acid  with  hydriodic  acid.     (This  will 
be  explained  under  Lactic  Acid,  which  see.) 

(2)  By  the  action  of  carbon  dioxide  upon  sodium  ethyl :  — 

C02  +  NaC2H5  =  C2H5 .  C02ISra. 

It  is  a  colorless  liquid  with  a  penetrating  odor  somewhat 
resembling  that  of  acetic  acid.  It  boils  at  141°.  (Compare 
with  boiling-points  of  formic  and  acetic  acids.) 


132  DERIVATIVES   OF  THE  PARAFFINS 

It  yields  a  large  number  of  derivatives  corresponding  to  those 
obtained  from  acetic  acid. 

NOTE  FOR  STUDENT.  —  What  is  propionyl  chloride  ?  and  how  can  it  be 
prepared?  It  is  analogous  to  acetyl  chloride. 

The  simple  substitution-products  of  propionic  acid  present 
an  interesting  and  instructive  case  of  isomerism.  There  are 
two  chlor-propionic  acids,  two  brom-propionic  acids,  etc.  Those 
products  which  are  obtained  by  direct  treatment  of  propionic 
acid  with  substituting  agents  are  called  a-products,  and  the 
isomeric  substances  /3-products.  Thus  we  have  a-chlor-propionic 
and  a-brom-propionic  acid,  made  by  treating  propionic  acid  with 
chlorine  and  bromine ;  and  f$- chlor-propionic  acid  and  ft-brom- 
propionic  acid,  made  by  indirect  methods.  The  difference  be- 
tween these  two  series  of  derivatives  is  due  to  different  relations 
between  the  constituents.  The  usual  method  of  representation 
indicates  the  possibility  of  the  existence  of  two  isomeric  chlor« 
propionie  acids,  and  of  similar  mono-substitution  products  of 
propionic  acid.  The  acid  is  represented  thus :  — 

CH3.CH2.C02H. 

Now,  if  chlorine  should  enter  into  the  compound,  as  represented 
by  the  formula  CH2C1.CH2.C02H,  (1)  we  should  have  one  of 
the  chlor-propionic  acids ;  while,  if  it  should  enter  as  indicated 
in  the  formula  CHg.CHCl.COaH,  (2)  we  should  have  the  iso- 
meric product.  We  have  thus  two  chlor-propionic  acids  actu- 
ally known,  and  our  theory  gives  us  two  formulas.  How  can 
we  tell  which  of  the  formulas  represents  a-chlor-propionic  acid, 
and  which  the  /?-acid  ?  Only  by  carefully  studying  all  the 
reactions  and  methods  of  formation  of  both  compounds.  The 
best  evidence  is  furnished  by  a  study  of  the  lactic  acids,  which 
will  be  shown  to  be  mono-substitution  products  of  propionic 
acid.  a-Chlor-propionic  acid  can  be  transformed  into  a  lactic 
acid,  the  structure  of  which  is  represented  by  the  formula 
CH8.CH(OH).C02H,  and  by  replacing  the  hydroxyl  of  this 


BUTYRIC   ACIDS  133 

lactic  acid  by  chlorine,  a-chlor-propionic  acid  is  formed.  It 
therefore  follows  that  formula  (2)  above  given  is  that  of  a-chlor- 
propionic  acid,  and  formula  (1)  that  of  /?-chlor-propionic  acid. 
Further,  any  mono-substitution  product  of  propionic  acid  that 
can  be  made  directly  from  a-chlor-propionic  acid,  or  converted 
directly  into  this  acid,  is  an  a-product,  and  has  the  general 
formula  CH8.CHX.C02H; 

and,  similarly,  the  ^-products  have  the  general  formula 

CH2X.CH2.C02H, 
in  which  X  represents  any  univalent  atom  or  group. 

Butyric  acids,  C4H8O2(C3H7 .  CO2H).  —  Normal  butyric 
acid,  butanic  acid,  CH3.  CH2.  CH2.  C02H.  When  butter  is 
boiled  with  caustic  potash,  the  potassium  salts  of  butyric  acid 
and  of  some  of  the  higher  members  of  the  series  are  found  in 
the  solution  at  the  end  of  the  operation.  Butter,  like  other 
fats,  belongs  to  the  class  of  compounds  known  as  ethereal 
salts ;  and  these,  as  we  have  seen,  when  boiled  with  the  alka- 
lies, are  decomposed,  yielding  alcohol  and  alkali  salts  of  acids 
(saponification).  In  the  case  of  butter  and  of  nearly  all  other 
fats,  the  alcohol  formed  is  glycerol.  Butyric  acid  occurs  also 
in  many  other  fats  besides  butter. 

It  is  most  readily  made  by  fermentation  of  sugar.  Sugar 
and  tartaric  acid  are  dissolved  in  water,  and,  after  a  time, 
putrid  cheese  and  sour  milk  are  added,  and  also  some  powdered 
chalk.  At  first  the  sugar  is  converted  into  glucose  and 
fructose :  — 

C12H2Ai  +  H20  =  C6H120  +  C6H1206. 

Cane  sugar  Glucose  Fructose 

The  glucose  is  then  converted  into  lactic  acid  by  the  lactic  acid 
ferment :  — 

C6H1206  =  2  C3H603. 

Glucose  Lactic  acid 


134  DERIVATIVES    OF   THE   PARAFFINS 

And,  finally,  the  lactic  acid  is  converted  into  butyric  acid  by 
the  butyric  acid  ferment  :  — 

2  C3H603  =  C4H802  -f  2  C02  -f  4  H. 

Other  methods  for  the  preparation  of  butyric  acid  are  :  —  - 

(1)  By  oxidation  of  normal  butyl  alcohol  ;  and 

(2)  By  treating  normal  propyl  cyanide,   CH3.CH2.CH2CN, 
with  caustic  potash. 

The  acid  is  a  liquid  having  an  acid,  rancid  odor,  like  that  of 
rancid  butter.  It  boils  at  163°.  (Compare  with  the  preceding 
acids.)  Like  the  lower  members  of  the  series  it  mixes  with 
water  in  all  proportions. 

Ethyl  butyrate,  C3H7.C02C2H5,  has  a  pleasant  odor  resembling 
that  of  pineapples.  It  is  used  under  the  name  of  essence  oj 
pineapples. 

Isobutyric  acid,  methyl-propanic  acid,r,T,3>CH.CO2H. 


•  —  From  the  two  propyl  alcohols  the  two  chlorides,  propyl  chlo- 
ride, CH3.CH2.CH2C1,  and  isopropyl  chloride,  ^>CHC1,  can 
be  made,  and  from  these  the  corresponding  cyanides,  — 
Propyl  cyanide    .....     CH3.CH2.  CHaCN, 

and      Isopropyl  cyanide  .     .     ^ 


When  boiled  with  caustic  potash,  the  former  is  converted  into 
normal  butyric  acid,  as  stated  above;  while  the  latter  yields 

isobutyric  acid,  ™3>CH.C02H.     This  acid   can   also  be   pre- 

C*  1-T 

pared  by  oxidizing  isobutyl  alcohol,  ~H3>CH.CH2OH.     It   is 
found  in  nature  in  the  carob  bean. 

Isobutyric  acid  is  a  liquid  which  boils  at  154°.  Its  odor  is 
less  unpleasant  than  that  of  the  normal  acid 

Valeric  acids,  C5H10O2(C4H9.CO2H).  —  Four  carboxyl  de- 
rivatives of  the  butanes  are  possible.  Four  acids  of  the 
formula  C5H1002  are  known. 


STEARIC   ACID  135 

f'TT 

Inactive  or  ordinary  valeric  acid,  CH3>CH.CH2.CO2H. 

—  This  acid  is  made  by  oxidizing  inactive  amyl  alcohol.  It 
can  also  be  made  (and  this  reaction  reveals  the  structure  of 

PTT 

the  acid)  by  starting  with  isobutyl  alcohol,  CH3>CH.CH2OH, 
converting  this  first  into  the  chloride  and  then  into  the  cya- 

fTT 

nide,  and,  finally,  transforming  the  cyanide,  CTj3>CH.CH2CN, 

into  the  acid.  It  occurs  in  valerian  root,  whence  its  name.  It 
is  an  unpleasant  smelling  liquid,  boiling  at  174°.  It  requires 
thirty  parts  of  water  for  solution. 

Amyl  valerate,  C4H9.C02C5Hn,  has  the  odor  of  apples,  and  is 
used  under  the  name  of  essence  of  apples. 

Active   valeric  acid,   „    *>CH.CH2.CH3.  —  This  acid 


is  prepared  by  oxidation  of  active  amyl  alcohol.  Although  the 
alcohol  turns  the  plane  of  polarization  to  the  left,  the  acid 
turns  it  to  the  right.  The  alcohol  is  said  to  be  levo-rotatory, 
and  the  acid  dextro-rotatory. 


The  higher  acids  of  the  series  are,  for  the  most  part,  found 
in  various  fats.  They  are  difficultly  soluble  in  water.  The 
highest  members  are  solids.  The  two  best  known,  because 
occurring  in  largest  quantity,  are  palmitic  and  stearic  acids. 
These  are  contained  in  combination  with  the  alcohol,  glycerol, 
in  all  the  common  fats.  The  fats  will  be  treated  of  under 
Glycerol. 

Palmitic  acid,  C15H31.C(XH,  can  be  made  by  saponifying 
many  fats,  as  palm  oil,  olive  oil,  and  bay  berry  tallow.  The 
last-named  fat  consists  of  about  one-fifth  part  of  palmitin,  four- 
fifths  being  free  palmitic  acid  and  a  little  lauric  acid  and  laurin. 

It  crystallizes  in  needles  which  melt  at  62.6°. 

Stearic  acid,  C17H35.C(XH,  is  the  acid  contained  in  that 
particular  fat  known  as  stearin*  The  so-called  "stearin  can- 


136  DERIVATIVES   OF  THE  PARAFFINS 

dies"  consist  of  stearic  acid  mixed  with  palmitic  acid  and  a 
little  paraffin,  and  from  them  stearic  acid  can  be  separated  in 
pure  form  by  long-continued  fractional  crystallization  from 
ether  and  alcohol. 

It  crystallizes  from  alcohol  in  needles  or  laminae  which  melt 
at  69.3°. 

Soaps.  —  In  speaking  of  the  decompositions  of  ethereal  salts 
by  boiling  with  alkalies,  it  was  stated  that  this  process  is  called 
saponification  because  it  is  best  exemplified  in  the  manufacture 
of  soaps  from  fats.  The  fats  are  themselves  rather  complicated 
ethereal  salts.  When  they  are  boiled  with  an  alkali,  as  caustic 
soda,  the  alcohol  is  liberated,  and  the  alkali  salts  of  the  acids 
are  formed.  These  salts  are  the  soaps.  They  are  in  solution  after 
the  process  of  saponification  is  completed,  and  can  be  separated 
by  adding  a  solution  of  common  salt,  in  which  they  are  insoluble. 

Experiment  33.  Dissolve  10s  caustic  potash  in  150CC  of  alcohol  in 
a  250CC  flask  and  filter.  Melt  in  a  porcelain  dish  on  a  water-bath  10e 
of  lard  and  then  add  the  alcoholic  solution  of  potassium  hydroxide. 
Evaporate  to  syrupy  consistency  slowly  on  a  water-bath,  with  constant 
stirring.  The  residue  is  soap.  Dissolve  some  of  the  soap  thus  obtained  in 
water,  and  filter.  Add  hydrochloric  acid,  when  the  free  fatty  acids, 
mainly  palmitic  and  stearic  acids,  will  separate  as  solids,  which  will  rise 
to  the  top.  The  hydrochloric  acid  simply  decomposes  the  sodium  pahni- 
tate  and  stearate,  giving  free  palmitic  and  stearic  acids  and  sodium 
chloride :  — 

Ci5H31.C02Na  +  HC1  =  Ci5H31.C02H  +  NaCl, 

Sodium  palmitate  Palmitic  acid 

and  Ci7H35.CO2Na  -1-  HC1  =  Ci7H35.CO2H  +  NaCl. 

Sodium  stearate  Stearic  acid 


The  remaining  derivatives  of  the  higher  members  of  the 
paraffin  series  include  the  ethers,  ketones, '  ethereal  salts, 
mercaptans,  sulphur  ethers,  sulphonic  acids,  cyanides  arid 
isocyanides,  cyanates  and  isocyanates,  sulpho-cyanates  and 
iso-sulpho-cyanates,  substituted  ammonias  and  analogous  com- 
pounds, metal  derivatives,  and  nitro-derivatives. 


ETHYLENE   ALCOHOL  137 

A  great  many  substances  belonging  to  these  classes,  and 
containing  residues  of  the  higher  hydrocarbons,  have  been  pre- 
pared and  studied ;  but,  in  the  main,  they  so  closely  resemble 
the  simpler  substances  which  have  already  been  described  that 
we  should  gain  nothing  by  taking  them  up  here  individually. 
The  student,  however,  is  earnestly  advised  to  apply  the  princi- 
ples discussed  in  the  first  part  of  the  book  to  a  few  other  cases. 
Thus,  let  him  take  propane  and  butane,  and  not  only  write  the 
formulas  of  the  derivatives  which  can  be  obtained  from  them, 
but,  above  all,  write  the  equations  representing  the  action  in- 
volved in  their  preparation,  and  the  transformations  of  which 
they  are  capable. 

POLYACID   ALCOHOLS   AND   POLYBASIC  ACIDS 
1.   DI-ACID  ALCOHOLS 

The  alcohols  thus  far  treated  of  are  of  the  simplest  kind. 
They  correspond  to  the  simplest  metallic  hydroxides,  as  potas- 
sium hydroxide,  KOH.  Just  as  these  simplest  metallic  hydrox- 
ides are  called  mon-acid  bases,  so  the  simplest  alcohols  are 
called  mon-acid  alcohols^  expressions  which  are  suggested  by 
the  term  mono-basic  acid.  But,  as  is  well  known,  there  are 
metallic  hydroxides,  like  calcium  hydroxide,  Ca(OH)2,  barium 
hydroxide,  Ba(OH)2,  etc.,  which  contain  two  hydroxyls,  and 
are  hence  known  as  di-acid  bases;  and  so,  too,  there  are  di-acid 
alcohols  which  bear  to  the  mon-acid  alcohols  the  same  relation 
that  the  di-acid  bases  bear  to  the  mon-acid  bases.  Only  one 
alcohol  of  this  kind,  derived  from  the  paraffin  hydrocarbons,  is 
well  known. 

Ethylene  alcohol  or  gly col,  ethandiol,  C2H6O2[C2H4(OH)2]. 

—  Glycol  is  made  by  starting  with  ethylene,  a  hydrocar- 
bon of  the  formula  C2H4.  When  this  is  brought  together 
with  bromine,  the  two  unite  directly,  forming  ethylene  bromide, 

1  The  expression  monatomic  alcohols  is  used  by  some  writers,  but,  as  it  is  confusing, 
it  is  giving  way  to  the  more  rational  expression  above  used. 


138  DERIVATIVES    OF   THE   PARAFFINS 

C2H4Br2.  By  replacing  the  two  bromine  atoms  by  hydroxyl, 
ethylene  alcohol  or  glycol  is  formed. 

It  is  a  colorless,  inodorous,  somewhat  oily  liquid,  that  boils 
at  197.5°.  It  has  a  sweetish  taste,  and  is  hence  called  glycol 
(from  yXvKvs,  sweet).  Hence,  further,  the  other  alcohols  of  this 
series  are  also  called  glycols. 

The  derivatives  of  ethylene  alcohol  are  not  as  numerous  as 
those  of  the  better-known  members  of  the  methyl  alcohol  series, 
but  those  which  are  known  are  of  the  same  general  character. 
The  reactions  of  the  alcohol  are  the  same  as  those  of  the  mon- 
acid  alcohols,  but  it  presents  more  possibilities.  In  most  cases 
in  which  a  mon-acid  alcohol  yields  one  derivative,  ethylene 
alcohol  yields  two.  Thus,  with  sodium,  the  two  compounds, 

ONa  ONa 

sodium  glycol,  C2H4<        ,   and   di-sodium  glycol,  C2H4<        , 
OJtl  O.Na 

can  be  formed ;  from  these,  by  treating  with  ethyl  iodide,  the 

/~\/"1     TT 

two  ethers,  ethyl-glycol  ether,  C2H4<      2   6,  and  di-ethyl- glycol 

OC1  H 

ether,  C2H4<      2TT5,  are  made.     By  treatment  with  hydrochloric 

OL2H.5 

Cl 

acid,  the  chloride,  C2H4<       ,  known  as  ethylene  chlorhydrin,  is 

OH 

formed;  and  this,  by  treatment  with  phosphorus  trichloride, 
can  be  converted  into  ethylene  chloride,  C2H4C12,  etc. 

Its  conduct  towards  acids  is  like  that  of  a  di-acid  base.  It 
forms  neutral  and  alcoholic  salts,  of  which  the  acetates  may  serve 
as  examples.  Thus  we  have  the 

Mono-acetate,  G2H4<  ^CT2H3°, 
OH 

and  the  Di-acetate,       C2H4< 

2x3 

the  former  still  containing  alcoholic  hydroxyl  and  corresponding 
to  a  basic  salt;  the  latter  being  a  neutral  compound. 

The  formation  of  the  di-acetate  is  a  step  in  one  of  the  methods 
of  preparing  ethylene  alcohol.  This  method  consists  in  treat- 
ing ethylene  bromide  with  potassium  acetate  in  alcoholic  solu- 


ETHYLENE   ALCOHOL  139 

tion,  separating  the  acetate  of  ethylene  thus  formed,  and 
decomposing  it  by  means  of  barium  hydroxide.  The  reactions 
involved  are  represented  by  the  following  equations  :  — 


Br     KO.C2H30  0.  C2H30 

S^^^ 

The  alcohol  can  also  be  made  by  treating  ethylene  bromide 
with  potassium  carbonate:  — 


and  by  treating  ethylene  bromide  with  silver  oxide  :  — 


C2H4  <       +  Ag20  +  H20  =  C2H4  <    :    +  2  AgBr. 
±>r  Un. 

These  methods  of  formation  show  clearly  what  ethylene 
alcohol  is. 

When  acetyl  chloride  acts  upon  the  alcohol  at  ordinary  tem- 

perature, the  product  has  the   formula  C2H4  <  ^p11'0.      This 

is  also  formed  by  the  action  of  hydrochloric  acid  gas  on  the 
di-acetate.  It  seems  probable,  therefore,  that  the  action  of 
acetyl  chloride  should  be  represented  by  two  equations,  thus  :  — 

C«H'  <  nw  +  2  C2H'OC1  =  C"H*  <  np2w3n  +  2  HC1  5 

UU2ri3D 

and      C2H4  <  OC2H30  +  Ha  =  p^  <  OC2H30  +  c  ^^ 
UO2rl3U 

There  are  two  ways  in  which  the  structure  of  a  compound 
of  the  formula  C2H4(OH)2  can  be  represented.     These  are,  — 

CH2(OH) 
(1)    |  ,  in  which  each  hydroxyl  is  represented  in  combi- 

CH2(OH)  CH(OH)2  m 

nation  with  a  different  carbon  atom  ;  and  (2)  I  ,  in  which 


140  DERIVATIVES   OF   THE   PARAFFINS 

both  hydroxyls  are  represented  in  combination  with  the 
same  carbon  atom.  The  question  suggests  itself,  to  which  of 
these  formulas  does  ethylene  alcohol  correspond  ?  To  answer 
this  question,  we  must  recall  what  was  said  regarding  the  two 
dichlor-ethanes,  known  as  ethylene  chloride  and  ethylidene 
chloride.  The  former  of  these  corresponds  to  the  formula 
CH2C1.CH2C1,  while  the  latter,  which  is  formed  from  aldehyde 
by  replacing  the  carbonyl  oxygen  by  two  chlorine  atoms,  is 
represented  by  the  formula  CHC12.CH3.  When  the  chlorine 
atoms  of  ethylene  chloride  are  replaced  by  hydroxyl,  ethylene 
alcohol  is  produced.  Hence,  the  alcohol  has  the  formula 
(HO)H2C  —  CH2(OH),  or  each  of  the  hydroxyls  is  in  combina- 
tion with  a  different  carbon  atom.  When  oxidized,  ethylene 

CH2OH 

alcohol  gives,  first,  glycolic  acid,  I  .  and  then  oxalic  acid, 
COOH  COOH 

I  -  This  furnishes  independent  evidence  that  the  alcohol 
COOH 

contains  two  primary  alcohol  groups  and  it  must  therefore  be 

CH2OH 
represented  by  the  formula   | 

CH2OH 

All  attempts  to  make  the  isomeric  di-acid  alcohol  correspond- 
ing to  ethylidene  chloride,  and  having  both  hydroxyls  in  com- 
bination with  the  same  carbon  atom,  as  represented  in  the 

CH(OH)2 
formula  I  ,  have  failed.     Instead  of  getting  ethylidene 

CHg 

alcohol,  aldehyde  is  generally  obtained.  Aldehyde  is  ethyli- 
dene alcohol  minus  water :  — 

CH3  -  CH(OH)2  =  CH3  -  CHO  +  H20. 

It  is  believed  that  one  carbon  atom  cannot,  under  ordinary 
circumstances,  hold  in  combination  more  than  one  hydroxyl 
group.  If  this  is  true,  then  ethylidene  alcohol  cannot  be  pre- 

OFT 

pared  any  more  than  the  hypothetical  carbonic  acid,  CO<  Q  , 
can  be.  So,  too,  the  simplest  di-acid  alcohol  conceivable, 


ETHYLENE   ALCOHOL  141 

viz.,  methylene  alcohol,   CH2(OH)2,   cannot  exist,  but   would 
break  up,  if  formed  at  all,  into  water  and  formic  aldehyde :  — 

CH2(OH)2  =  H20  +  H.CHO. 

(See  discussion  regarding  the  transformation  of  alcohol  into 
aldehyde,  pp.  65-67.) 

Ethyl  alcohol,  as  was  pointed  out,  may  be  regarded  either  as 
ethane  in  which  one  hydrogen  is  replaced  by  hydroxyl,  or  as 
water  in  which  one  hydrogen  is  replaced  by  ethyl.  Ethyl,  like 
all  the  radicals  contained  in  the  mon-acid  alcohols,  is  univcdent. 
It  is  ethane  less  one  atom  of  hydrogen,  just  as  methyl  is  methane 
less  one  atom  of  hydrogen.  Each  has  the  power  of  uniting  with 
one  atom  of  hydrogen,  or  another  univalent  element,  or  of  tak- 
ing the  place  of  one  atom  of  hydrogen. 

If  we  take  away  two  atoms  of  hydrogen  from  methane  and 
ethane,  we  have  left  the  residues  or  radicals  CH2  and  C2H4. 
These  can  unite  with  two  atoms  of  hydrogen,  or  take  the  place 
of  two  atoms  of  hydrogen,  and  they  are  hence  called  bivalent 
radicals. 

Just  as  ethylene  alcohol  may  be  regarded  as  ethane  in  which 
two  hydrogen  atoms  are  replaced  by  hydroxyls,  so  it  may  be 
regarded  as  water  in  which  the  bivalent  radical  ethylene  re- 
places two  hydrogens  belonging  to  two  different  molecules  of 
water :  — 

H-O-H    H-O-H  H-0-C2H4-0-H 

Two  molecules  water  Ethylene  alcohol 


The  higher  member  of  the  series  of  di-acid  alcohols  will  not 
be  taken  up  here. 

2.   DIBASIC  ACIDS 

Just  as  there  are  di-acid  alcohols  derived  from  the  paraffins, 
so  there  are  dibasic  acids  which  may  also  be  regarded  as  deriva- 
tives of  the  paraffins.  We  have  seen  that  the  simplest  acids, 
the  monobasic  fatty  acids,  are  closely  related  to  formic  and 


142  DERIVATIVES   OF  THE   PARAFFINS 

carbonic  acids  ;  that  they  may  be  regarded  as  derived  from  the 
latter  by  replacement  of  a  hydroxyl  by  a  radical,  or  as  derived 
from  the  paraffins  by  the  introduction  of  the  group  carboxyl, 
C02H.  The  conditions  existing  in  this  group  are  essential  to 
the  acid  properties.  If  two  carboxyls  are  introduced  into  marsh 
gas,  a  substance  of  the  formula  CH2(C02H)2  is  formed,  and 
this  is  a  dibasic  acid.  It  contains  two  acid  hydrogens,  and 
is  capable  of  forming  two  series  of  salts,  the  acid  and  neutral 
salts,  like  other  dibasic  acids.  It  may  be  regarded  also  as 
derived  from  two  molecules  of  carbonic  acid  by  the  replacement 
of  two  hydroxyls  by  the  bivalent  radical  CH2  :  — 


Two  molecules  carbonic  acid  Dibasic  acid 

The  general  methods  of  preparation  available  for  the  building 
up  of  the  series  of  dibasic  acids  are  modifications  of  those  used 
in  making  the  monobasic  acids.  They  are  :  — 

1.  Oxidation  of  di-acid  primary  alcohols.     Just  as  a  mon- 
acid  primary  alcohol,  R.CH2OH,  yields  by  oxidation  a  mono- 
basic acid,  so  a  di-acid  primary  alcohol,  R"(CH2OH)2,  yields  a 
dibasic  acid,  K"(C02H)2. 

2.  Treatment  of  the  dicyanides,  R"(CN)2,  with  caustic  alkalies. 

3.  Oxidation  of  the  hydroxy-acids  or  alcohol  acids.     These 
are  compounds  which  are  at  the  same  time  alcohol  and  acid; 
as,  for  example,  hydroxy-acetic  acid,  which  is  acetic  acid  in 
which  one  of  the  hydrogen  atoms  of  the  hydrocarbon  residue, 
methyl,  has  been  replaced  by  hydroxyl,  as  represented  in  the 

CH2OH 
formula    |  •    When  this  is  oxidized,  the  alcoholic  portion, 

C02H 
CH2OH,  is  converted  into  carboxyl,  and  a  dibasic  acid  is  formed. 

4.  From  the  cyanogen  derivatives  of  the  monobasic  acids, 


OXALIC    ACID 


143 


such  as  cyan-acetic  acid,  CH2  <  co  H  ,  by  the  transformation  of 
the  cyanogen  group  into  carboxyl. 


Oxalic 

Malonic  " 

Succinic  " 
Pyrotartaric  " 

Adipic  « 

Pimelic  « 

Suberic  « 

Azelaic  " 

Sebacic  « 

Brassylic  " 

Eoccellic  " 


DIBASIC   ACIDS, 

acid 


(C02H)2. 

CH2(C02H)2. 

C2H4(C02H)2. 

C3H6(C02H)2. 

C4H8(C02H)2. 

C5H10(C02H)2. 

C6H12(C02H)2. 

C7H14(C02H)2. 

C8H16(C02H)2. 

C9H18(C02H)2. 


Of  the  many  acids  included  in  this  list  only  four  or  five  can 
be  said  to  be  well  known.  We  may  confine  our  attention  to  the 
first  four  members. 


Oxalic  acid,  CoHsCMCCC^H^].  —  In  one  sense,  according  to 
the  accepted  definition,  oxalic  acid  is  not  a  member  of  the  series 
with  which  we  are  dealing,  as  it  is  not  derived  from  a  hydro- 
carbon by  replacement  of  hydrogen  by  carboxyl;  nor  is  it 
derived  from  two  molecules  of  carbonic  acid  by  replacement  of 
two  hydroxyls  by  a  bivalent  radical.  Still  it  is  in  other  respects 
so  closely  allied  to  the  members  of  the  series,  and  has  so  many 
things  in  common  with  the  other  members,  that  it  would  be  a 
mere  act  of  pedantry  to  consider  it  in  any  other  connection. 

Oxalic  acid  occurs  very  widely  distributed  in  nature  ;  as  in 
certain  plants  of  the  oxalis  varieties,  in  the  form  of  the  acid 


144  DERIVATIVES   OF  THE  PAKAFFINS 

potassium  salt;   as  calcium  salt  in  many  plants;   in  urinary 
calculi;  and  as  the  ammonium  salt  in  guano. 

It  is  formed  by  the  action  of  nitric  acid  upon  many  organic 
substances,  particularly  the  different  varieties  of  sugar  and  the 
so-called  carbohydrates,  such  as  starch,  cellulose,  etc. 

Experiment  34.  To  be  carried  out  under  a  hood.  In  a  good-sized 
flask  pour  half  a  litre  of  ordinary  concentrated  nitric  acid  (of  specific 
gravity  1.245)  upon  50&  of  sugar.  Heat  gently  until  the  reaction  begins. 
Then  withdraw  the  flame,  when  the  oxidation  will  proceed  with  some 
violence,  and  accompanied  by  a  copious  evolution  of  red  fumes.  When 
the  action  has  ceased,  evaporate  the  liquid  to  one-sixth  the  original 
volume,  and  let  it  cool,  when  oxalic  acid  will  crystallize  out.  Recrystal- 
lize  from  water  the  acid  thus  obtained,  and  with  the  pure  substance 
perform  such  experiments  as  will  exhibit  its  properties.  For  example, 
(1)  Heat  a  specimen  at  100°,  and  notice  loss  of  water;  (2)  Heat  some  in 
a  small  flask  with  sulphuric  acid,  and  show  that  both  oxides  of  carbon 
are  formed. 

On  the  large  scale,  oxalic  acid  is  made  by  heating  wood 
shavings  or  sawdust  with  caustic  potash  and  caustic  soda  to 
240°  to  250°.  The  mass  is  extracted  with  water,  and  the  solu- 
tion evaporated  to  -crystallization,  when  sodium  oxalate  is 
deposited. 

Other  methods,  which  are  interesting  from  a  purely  scientific 
point  of  view,  are  the  following  :  — 

1.  The  spontaneous  transformation  of  an  aqueous  solution  of 
cyanogen  :  — 

CN  C02H 

I      +4H20=|          +  2NH3; 
C02H 

C02(NH4) 
or,  really,  |      +  4  H20  =  | 

CN  C02(NH4) 

2.  Treatment  of  carbon  dioxide  with  sodium  :  — 


3.   Heating  sodium  formate  :  — 

2  H  .  C02Na  =  C204Na2  +  2  H. 


MALONIC   ACID  145 

Oxalic  acid  crystallizes  from  water  in  xnonoclinic  prisms  con- 
taining two  molecules  of  water  (C2H204  +  2  H20).  It  loses 
this  water  at  100°,  and  then  melts  at  189°.  It  sublimes  just 
above  the  melting-point,  but,  if  heated  higher,  it  breaks  up 
into  carbon  monoxide,  carbon  dioxide,  and  formic  acid :  — 

2  C2H204  =  2  C02  +  CO  +  HC02H  +  H20. 

Sulphuric  acid  decomposes  it  into  carbon  monoxide,  carbon 
dioxide,  and  water.  Heated  with  glycerol  to  100°,  carbon 
dioxide  and  formic  acid  are  formed  (see  Formic  Acid) :  — 

C2H204  =  C02  +  HC02H. 

It  is  an  excellent  reducing  agent,  and  is  used  to  standardize 
solutions  of  potassium  permanganate. 

Experiment  35.  Try  the  action  of  a  solution  of  potassium  perman- 
ganate on  a  solution  of  oxalic  acid.  Why  is  it  best  to  have  the  solution 
of  the  permanganate  acid  ? 

Oxalic  acid  is  an  active  poison.    It  is  used  in  calico  printing. 

Salts  of  oxalic  acid.  Like  all  dibasic  acids,  oxalic  acid  forms 
acid  and  neutral  salts  with  metals.  All  the  salts  are  insoluble 
except  those  containing  the  alkalies.  Among  those  most  com- 
mon are  the  acid  potassium  salt,  C204HK,  which  is  found  in  the 
sorrels  or  plants  of  the  oxalis  variety;  the  ammonium  salt, 
C204(NH^2)  of  which  some  urinary  calculi  consist;  and  cal- 
cium oxalate,  C204Ca,  which,  being  insoluble  in  water  and 
acetic  acid,  is  used  as  a  means  of  detecting  calcium  in  the  pres- 
ence of  magnesium,  and  of  estimating  calcium  and  oxalic  acid. 

Malonio  acid,  C3H4O4[CH2(CO2H)2].  —  This  acid  was  first 
made  by  oxidation  of  malic  acid  (which  see),  and  is  hence 
called  malonic  acid.  It  can  best  be  made  by  starting  with 
acetic  acid.  The  necessary  steps  are :  (1)  making  chlor-acetic 
acid ;  (2)  transforming  chlor-acetic  acid  into  cyan-acetic  acid ; 
(3)  heating  cyan-acetic  acid  with  an  alkali. 

NOTE  FOR  STUDENT.  —  Write  the  equations  representing  the  three 
steps  mentioned. 


146  DERIVATIVES    OF    THE   PARAFFINS 

It  is  a  solid  that  crystallizes  in  laminae.  It  breaks  up  at  a 
temperature  above  132°,  which  is  its  melting-point,  into  carbon 
dioxide  and  acetic  acid  :  — 


CH2  <  ;;2  =  CH3co2H  +  coa. 
\j(j2t± 

When  heated  under  certain  conditions  it  yields  a  product  of 
the  composition,  C302,  which  is  called  carbon  suboxide  or  ma- 
Ionic  anhydride. 

Succinic  acids,  C4H6O4[C2H4(CO2H)2].  —  Regarding  these 
acids  as  derived  from  ethane  by  substituting  two  carboxyls  for 
two  hydrogens,  it  is  clear  that  two  are  possible,  one  corre- 
sponding to  ethylene  chloride  and  another  corresponding  to 
ethylidene  chloride.  Two  are  actually  known.  One  is  the 
well-known  succinic  acid  ;  the  other  is  called  isosuccinic  acid. 

CH2.CO2H 

Succinic   acid,  ethylene-succinic   acid,    |  .  — 

CH2.C02H 

This  acid  occurs  in  amber  (hence  its  name,  from  Lat.  succinum, 
amber);  in  some  varieties  of  lignite  ;  in  many  plants  ;  and  in 
the  animal  organism,  as  in  the  urine  of  the  horse,  goat,  and 
rabbit. 

It  is  formed  under  many  circumstances,  especially  by  oxida- 
tion of  fats  with  nitric  acid,  by  fermentation  of  calcium  malate, 
and,  in  small  quantity,  in  the  alcoholic  fermentation  of  sugar. 
Among  the  methods  for  its  preparation  are  :  — 

CH2.C£T 

1.   Treatment  of  ethylene  cyanide,   |  ,  with  a  caustic 

alkali:—  CH2.CN 


CH2.C02K 
20  =  | 
CH2CN  CH2.C02K 

2.    Similarly,  by  treatment  of  /?-cyan-propionic  acid  with  an 
alkali.     (What  is  /?-cyan-propionic  acid?) 


ISOSUCCINIC   ACID  147 

3.  Reduction  of  tartaric  and  malic  acids  by  means  of  hy- 
driodic  acid.  These  well-known  acids  will  be  shown  to  be 
closely  related  to  succinic  acid,  and  the  reaction  here  mentioned 
will  be  explained.  The  methods  actually  used  in  the  prepara- 
tion of  succinic  acid  are :  (1)  the  distillation  of  amber,  and 
(2)  the  fermentation  of  calcium  malate. 

The  acid  crystallizes  in  monoclinic  prisms,  which  melt  at 
182°  (try  it).  It  boils  at  235°,  at  the  same  time  giving  off 
water,  and  yielding  the  anhydride:  — 

COOH      rH   .CO 
C2H4<COOH  =  C2H4<C()>  )  +  H20. 

Succinic  anhydride  is  a  solid  substance  that  crystallizes  well 
from  chloroform.  It  is  converted  into  succinic  acid  by  boiling 
with  water.  When  boiled  with  alcohols  it  yields  the  corre- 
sponding ester  acids.  For  example,  with  ordinary  alcohol 
mono-ethyl  succinate  is  formed. 

C2H4<£°>0  +  C2H5OH  = 

Among  the  salts  basic  ferric  suctinate,  C4H404.  Fe(OH),  is  of 
special  interest,  as  it  is  entirely  insoluble  in  water,  and  can 
therefore  be  used  for  the  purpose  of  separating  iron  and 
aluminium  from  manganese,  zinc,  nickel,  and  cobalt  quanti- 
tatively. 

Experiment  36.  Make  a  neutral  solution  of  ammonium  succinate 
by  neutralizing  an  aqueous  solution  of  the  acid,  and  boiling  off  all  excess 
of  ammonia.  Add  some  of  this  solution  to  a  solution  known  to  contain 
manganese  and  iron  in  the  ferric  state.  A  brown-red  precipitate  will  be 
formed.  Filter  and  wash,  and  examine  the  filtrate  for  iron. 

CH(C02H)t 

Isosuccinic  acid,  ethylidene-succinic  acid,   I 

CH3 

This  acid  is  made  by  treating  a-cyan-propionic  acid  with  an 
alkali.     (What  is  a-cyan-propionic  acid  ?) 

Isosuccinic  acid  forms  crystals  that  melt  at  130°.     Heated 


148  DERIVATIVES   OF   ^HF   PARAFFINS 

above  its  melting-point  it  breaks  up  into  propionic  acid  and 
carbon  dioxide:  — 

CH(C02H)2      CH2C02H 

I  =1  +CO* 

CH3  CH3 

Isosuccinic  acid  Propionic  acid 

NOTE  FOR  STUDENT.  —  Notice  carefully  the  difference  between  the  two 
succinic  acids,  as  shown  by  their  conduct  when  heated.  What  is  the 
difference  ? 

Acids  of  the  formula  C5H8O4[C3H6(CO2H)2].  -—  Four 
acids  of  the  formula  C5H804  are  known,  only  one  of  which, 
however,  need  be  mentioned  here.  This  is, — 

CH3.CH.CO2H 

Pyrotartaric  acid,  As  the  name  indi- 

CH2.CO2H 

cates,  this  acid  may  be  made  by  dry  distillation  of  tartaric  acid. 

TRI-ACID  ALCOHOLS 

The  existence  of  mon-acid  alcohols  corresponding  to  the  mon- 
acid  bases,  like  potassium  hydroxide,  and  of  di-acid  alcohols 
corresponding  to  the  di-acid  bases,  like  calcium  hydroxide,  sug- 
gests the  possible  existence  of  tri-add  alcohols  corresponding  to 
tri-acid  bases,  like  ferric  hydroxide.  There  is  only  one  alcohol 
of  this  kind  derived  from  the  paraffin  hydrocarbons  that  is  at  all 
well  known.  This  is  the  common  substance  glycerin  or  glycerol. 

Glycerol,  glycerin,  propantriol,  C3H8O3.  —  As  has  been 
stated  repeatedly,  glycerol  occurs  very  wfdely  distributed  as  the 
alcoholic  or  basic  constituent  of  the  fats.  The  acids  with  which 
it  is  in  combination  are  mostly  members  of  the  fatty  acid  series, 
though  one,  ole'ic  add,  which  is  found  frequently,  is  a  mem- 
ber of  another  series.  Besides  ole'ic  acid  the  two  acids  most 
frequently  met  with  in  fats  are  palmitic  and  stearic  acids. 
When  a  fat  is  saponified  with  caustic  potash,  it  yields  free 
glycerol  and  the  potassium  salts  of  the  acids.  The  reactions  in 


GLYCEROL  149 

the  case  of  the  glycerol  compounds  of  palmitic  and  stearic  acids 
are  these :  — 

Formation 

C3H5(OH)3+3  HO  .  00  .  C15H81=C3H6(0 .  00  .  CuHffl)8+3  H20. 

Gl^cerol  Palmitic  acid  Glyceryl  tri-palinitate, 

or  Palmitin 

C3H5(OH)3+  3  HO  .  00  .  0^=  C3H5(0 .  00  .  C17H35)3+3  H20. 

Glycerol  Stearic  acid  Glyceryl  tri-stearate, 

or  Stearin 

Saponification 
03H5(0  .  00  .  C15H31)3  +  3  KOH  =  C3H5(OH)3  +  3  C15H31 .  C02K. 

Palmitin  Glycerol  Potassium  palmitate 

C3H5(0  .  00  .  C17H35)3  +  3  KOH  =  C3H5(OH)3  +  3  (^H* .  C02K. 

Stearin  Glycerol  Potassium  stearate 

The  fats  are  also  decomposed  by  superheated  steam,  yield- 
ing free  glycerol  and  the  free  acids,  and  this  method  is  used 
on  the  large  scale,  a  little  lime  being  added  to  facilitate  the 
process.  Lead  oxide  decomposes  fats  yielding  a  mixture  of 
glycerol  and  the  lead  salts  of  the  acids.  The  mixture  is  known 
in  medicine  as  "  lead  plaster." 

Glycerol  is  formed  in  small  quantity  by  the  alcoholic  fer- 
mentation of  sugar. 

It  has  been  made  synthetically  from  propylene  chloride, 
C3H6C12.  The  necessary  steps  are:  (1)  treatment  with  chlo- 
rine, giving  C3H5C13 ;  (2)  treatment  of  the  tri-chlorine  deriva- 
tive with  water,  thus  replacing  the  three  chlorine  atoms  by 
hydroxyl :  — 

CH2C1  CH2C1  CHoOH 

I  I  I 

CHOI         — >-         CHOI         — ^         CHOH. 

I  I  I 

CH3  CH2C1  CH2OH 

(3)  Another  method  that  leads  to  the  artificial  preparation  of 
glycerol  consists  in  oxidizing  allyl  alcohol  (which  see).  This 
reaction  is  represented  thus  : 


150  DERIVATIVES   OF   THE  PARAFFINS 

C3H5OH  +  0  +  H20  =  C3H5(OH)3. 

Allyl  alcohol  -  Glycerol 

Glycerol  is  a  thick  colorless  liquid,  with,  a  sweetish  taste 
(compare  with  glycol).  It  mixes  with  alcohol  and  water  in 
all  proportions  but  is  insoluble  in  ether.  It  attracts  moisture 
from  the  air.  At  low  temperatures  it  slowly  solidifies,  form- 
ing deliquescent  crystals  which  melt  at  17°.  Pure  glycerol 
boils  at  290°  almost  without  decomposition.  If  salts  are  pres- 
ent, it  undergoes  decomposition  at  the  boiling  temperature.  It 
can,  however,  then  be  distilled  under  diminished  pressure.  It 
is  volatile  with  water  vapor.  It  does  not  evaporate  ;  it  attracts 
moisture  from  the  air  and  retains  its  oily  character ;  it  makes 
the  skin  soft  without  objectionable  results.  These  properties 
have  led  to  a  number  of  practical  applications  of  glycerol  as, 
for  example,  for  the  prevention  of  drying,  as  a  constituent  of 
soaps,  for  filling  gas  meters,  etc.,  but  its  chief  use  is  in  the 
manufacture  of  nitro-gtycerin, 

Experiment  37.  Heat  a  little  commercial  glycerol  in  a  dry  test- 
tube,  and  try  to  boil  it.  What  evidence  have  you  that  it  undergoes  de- 
composition ?  Put  20CC  to  30CC  glycerol  in  400CC  to  500CC  water  in  a  flask  ; 
connect  with  a  condenser,  and  boil.  Does  glycerol  pass  over  with  the 
water  vapor  ? 

The  reactions  of  glycerol  all  clearly  lead  to  the  conclusion 
that  it  is  a  tri-acid  alcohol. 

(1)  The  three  hydroxyl  groups  can  be  replaced  successively 
by  chlorine,  giving  the  compounds,  — 

(  Cl 
Chlorhydnn,       C3H5  j  /QJJ\  ; 

{Cl 
OH' 

and  Trtchlorhydrin,  C3H5C13. 

The  last  compound  is  really  trichlorpropane. 


GLYCEROL  151 

(2)  It  forms  three  classes  of  ethereal  salts  containing  one, 
two,  and  three  acid  residues  respectively.  For  example,  with 
acetic  anhydride  these  reactions  take  place :  — 

(  OC2H30 

1.  C3H5    OH  +  (C2H30)20   =  C3HJ  OH          +  C2H402. 

(OH 

(  OC2H30 

2.  C3H5-OH+2(C2H30)20  =  C3H5^OC2H30  +  2  C2H A- 

(OH 
f  OC2H30 

3.  C3H5    OH  -f  3  (C2H30)20  =  C3H5  J  OC2H30  +  3  C2H402- 

(  OH  (  OC2H30 

In  regard  to  the  relations  of  the  hydroxyl  groups  to  the  parts  of 
the  radical  C3H5,  it  appears  highly  probable  that  each  hydroxyl 
is  in  combination  with  a  different  carbon  atom  as  represented 
CH2OH 

in  the  formula  CHOH,  and  for  the  following  reasons  : 

CH2OH 

In  the  first  place,  it  has  been  shown  that  compounds  con- 
taining two  hydroxyls  in  combination  with  the  same  carbon 
are  unstable.  They  readily  lose  water.  It  would  follow  from 
this  that  the  simplest  tri-acid  alcohol  must  contain  at  least 
three  atoms  of  carbon,  just  as  the  simplest  di-acid  alcohol 
must  contain  at  least  two  atoms  of  carbon.  We  have  seen 
that  the  simplest  tri-acid  alcohol  known  does  contain  three 

atoms  of  carbon. 

CH2OH 
I 
Further,  if  the  formula  of  glj^erol  is  CHOH  ,  it  contains  two 

CH2OH 

primary  alcohol  groups,  CH2OH,  and  one  secondary  alcohol 
group,  CHOH,  and  we  have  seen  that  the  group  CH2OH  is 
converted  into  carboxyl  under  the  influence  of  oxidizing  agents ; 
and  the  group  CHOH  into  carbonyl  CO.  Therefore,  we  should 


152  DERIVATIVES   OF   THE  PARAFFINS 

expect  by  oxidizing  glycerol  to  get  products  of  the  formulas, 
C02H  C02H  COOH 

I  I  I 

CHOH  ,  CHOH,  and  CO      .    Products  of  these  formulas  actually 

II  I 
CH2OH    C02H             COOH 

are  obtained,  the  first  being  glyceric  acid  (which  see),  the  second 
tartronic  acid  (which  see),  and  the  third  mesoxalic  acid  (which 
see). 
Just  as  ethyl  alcohol  is  regarded  as  water  in  which  one 

/~1     TT       \ 

hydrogen  is  replaced  by  the  univalent  radical  C2H5,  as       j5  r  °  j 

and  glycol  is  regarded  as  water  in  which  two  hydrogen  atoms 
of  two  molecules  of  water  are  replaced  by  the  bivalent  radical 

H  ->0 
CoH4,  as  C2H4        •  so  also  glycerol  may  be  regarded  as  water 

H  >( 

in  which  three  hydrogen  atoms  of  three  molecules  are  replaced 
by  the  trivalent  radical  C3H5,  thus :  — 

HOH  [OH 

HOH  C8H5    OH. 

HOH  [OH 

Three  molecules  water  Glycerol 

Ethereal  salts  or  esters  of  glycerol.  —  Among  the  im- 
portant  esters   of  glycerol   are  the  nitrates.     Two   of  these 

(ONO2 
OH    ,    and  the  tri- 
OH 

nitrate,  C3H5(ON02)3,  the  latter  being  the  chief  constituent  of 
nitro-glycerin.  Nitre-glycerin  is  prepared  by  treating  glycerol 
with  a  mixture  of  concentrated  sulphuric  and  nitric  acids.  It 
is  a  pale  yellow  oil  insoluble  in  water.  At  low  temperatures 
it  crystallizes  in  long  needles.  It  explodes  very  violently  by 
concussion.  It  can  be  burned  in  an  open  vessel,  but  if  heated 
quickly  it  explodes.  The  products  of  the  chemical  change  that 
takes  place  are  carbon  dioxide,  steam,  and  free  nitrogen  which 
occupy  10,000  times  the  volume  of  the  •  nitro-glycerin.  This 


BUTTER  153 

fact,  together  with  the  ease  with  which  it  undergoes  decom- 
position, accounts  for  the  enormous  explosive  power  of  the 
substance.  Dynamite  is  infusorial  earth  impregnated  with 
nitro-glycerin.  Mixed  with  nitrocellulose  (which  see)  it 
forms  smokeless  powder.  It  is  the  active  constituent  of  other 
explosives. 

When  treated  with  a  caustic  alkali,  nitro-glycerin  is  saponi- 
fied, yielding  glycerol  and  a  nitrate.  This  shows  that  it  is  an 
ester  of  nitric  acid,  and  not  a  nitro-compound. 

Pats.  —  The  relation  of  the  fats  to  glycerol  has  already 
been  explained.  Most  fats  are  mixtures  of  the  three  neutral 
esters  that  glycerol  forms  with  palmitic,  stearic,  and  ole'ic 
acids,  known  by  the  names  palmitin,  stearin,  and  olein.  Olein 
is  liquid,  and  the  other  two  fats  are  solids,  stearin  having  the 
higher  melting-point.  Therefore,  the  larger  the  proportion  of 
olein  contained  in  a  fat,  the  softer  it  is,  while  the  larger  the 
proportion  of  stearin,  the  higher  the  melting-point.  Among 
the  fats  that,  are  particularly  rich  in  stearin  may  be  men- 
tioned mutton  tallow,  beef  tallow,  and  lard.  Human  fat  and 
palm  oil  are  particularly  rich  in  palmitin.  Sperm  oil  and  cod- 
liver  oil  are  rich  in  olei'n.  Pats  occur  very  widely  distributed 
in  nature,  both  in  plants  and  animals.  They  are  of  the  highest 
importance  from  the  physiological  point  of  view,  forming  one 
of  the  three  great  classes  of  food-stuffs. 

Butter  consists  of  ethereal  salts  of  glycerol  and  the  follow- 
ing acids :  myristic,  palmitic,  and  stearic  acids,  which  are  not 
volatile,  and  butyric,  caproi'c,  caprylic,  and  capric  acids,  which 
are  volatile  with  water  vapor.  All  the  acids  mentioned  are 
members  of  the  fatty  acid  series.  Some  of  these  acids  are  sol- 
uble and  some  are  insoluble  in  water.  The  percentage  of  in- 
soluble fatty  acids  contained  in  butter  has  been  found  to  be 
88  per  cent.  As  the  proportion  of  insoluble  fatty  acids  con- 
tained in  artificial  butters,  such  as  the  so-called  oleo-margarin, 


154  DERIVATIVES    OF   THE   PARAFFINS 

is  greater  than  that  contained  in  butter,  it  is  not  a  difficult 
matter  to  distinguish  between  the  two  by  determining  the 
amount  of  these  acids  contained  in  them. 

TRI-BASIC  ACIDS 

Tri-carballylic  acid,  C3H5(CO2H)3.  —  This  acid  can  be 
made  from  trichlorhydrin,  C3H5C13  (which  see),  by  replacing 
the  chlorine  by  cyanogen,  and  heating  with  an  alkali  the  tri- 
cyarihydrin  thus  obtained.  It  can  be  made  also  by  treating 
aconitic  acid  (which  see)  with  nascent  hydrogen.  It  crystal- 
lizes from  water  in  orthorhombic  prisms  which  melt  at  166°. 

TETR-ACID  ALCOHOLS 

Erythrol,  erythrite,  C4HioO4[C4H6(OH)4].  —  The  sub- 
stance occurs  in  one  of  the  algae  (Protococcus  vulgaris)  and  in 
several  lichens.  It  crystallizes  from  water  in  quadratic  prisms. 
It  has  a  very  sweet  taste.  The  fact  that  the  simplest  tetr-acid 
alcohol  contains  four  atoms  of  carbon  should  be  specially  noted. 


There  is   no   well-known   tetra-basic  acid  derived  from  the 
hydrocarbons  of  the  paraffin  series. 


PEXT-ACID  ALCOHOLS 

One  pent-acid  alcohol  occurs  in  nature  in  Adonis  vernalis, 
and  it  is  hence  called  adonite.  It  is  also  formed  by  reduction 
of  ribose  (which  see). 

By  reduction  of  xylose  (which  see)  a  pent-acid  alcohol,  called 
xylite,  is  formed;  and  by  reduction  of  arabinose  (which  see) 
another  called  arabite  is  formed. 

All  the  above-named  alcohols  have  the  formula  C5H1205 
[C5H7(OH)5].  There  are  three  modifications  of  arabite  —  two 
optically  active,  and  one  inactive.  There  is  still  another  pent- 
acid  alcohol  known  as  rhamnite,  formed  by  reduction  of  rham- 


HEX-ACID   ALCOHOLS  155 

nose  (which  see).     This  has  the  composition  represented  by 
the  formula  C6H1405[CH3.C5H6(OH)5]. 


Two  pentabasic  acids  have  been  made,  but  they  are  of  no 
special  importance. 

HEX-ACID  ALCOHOLS 

There  are  several  hex-acid  alcohols  known.  Most  of  them 
are  derived  from  hexane,  and  have  the  composition  represented 
by  the  formula  C6H8(OH)6.  It  will  be  noticed  that  these  hex- 
acid  alcohols  contain  six  carbon  atoms  each. 

Mannitol,  mannite,  C(iH8(OH)G.  —  Mannite  is  very  widely 
distributed  in  the  vegetable  kingdom.  It  occurs  most  abun- 
dantly in  manna,1  which  is  the  partly  dried  sap  of  the  manna-ash 
(Fraxinus  ornus),  a  tree  cultivated  in  Sicily.  It  is  obtained 
from  incisions  in  the  bark  of  the  tree.  Mannitol  makes  up  30  to 
60  per  cent  of  manna.  It  is  found  also  in  certain  mushrooms 
and  in  celery,  in  olives,  and  in  the  leaves  of  syringa  (mock 
orange)  and  in  many  other  plants.  It  forms  20  per  cent  of 
dried  Agaricus  integer. 

Mannite  is  formed  in  the  lactic  acid  fermentation  of  sugar. 
It  is  formed  also  by  the  action  of  nascent  hydrogen  on  fructose 
and  mannose.  It  crystallizes  in  needles,  or  rhombic  prisms, 
easily  soluble  in  water  and  in  alcohol.  It  has  a  sweet  taste. 

Nitric  acid  converts  mannite  into  manno-saccharic  acid 
(which  see).  When  boiled  with  concentrated  hydriodic  acid, 
it  is  converted  into  secondary  hexyl  iodide,  C6H]3I. 

Mannite  hexa-nitrate  (nitro-mannite),  C6H8(O.NO2)6,  is 
formed  by  treating  mannite  with  a  mixture  of  concentrated 
sulphuric  and  nitric  acids.  It  is  a  solid  substance  and  is  very 
explosive.  (Analogy  with  nitro-glycerin.) 

1  The  manna  of  the  Scriptures  was  probably  obtained  from  the  branches  of  Tammaria 
gallica.  It  contains  no  mannite,  but  a  fermentable  sugar. 


156  DERIVATIVES   OF   THE  PARAFFINS 

Mannite  hex-acetate,  C6H8(O.C2HSO)6,  is  formed  by  treat. 
ing  mannite  with  acetic  anhydride.  Its  formation,  as  well  as 
that  of  the  hexa-nitrate,  shows  that  mannite  is  a  hex-acid  alco- 
hol. The  number  of  acetyl  groups  that  enter  into  a  compound 
when  it  is  treated  with  acetic  anhydride  shows  how  many  hydroxyl 
groups  are  in  the  compound. 

There  are  three  varieties  of  mannite  —  the  ordinary,  known  as 
dextro-mannite,  and,  further,  levo-mannite,  and  inactive  mannite. 

Dulcite,  C6H8(OH)6.  —  This  occurs  in  a  kind  of  manna 
obtained  from  Madagascar,  the  source  of  which,  however,  is 
unknown.  It  is  formed  by  treating  sugar  of  milk  or  galactose 
with  nascent  hydrogen  (compare  with  raannite  in  this  respect). 

Nitric  acid  oxidizes  dulcite,  forming  rnucic  acid  (which  see), 
isomeric  with  manno-saccharic  acid,  which  is  formed  from 
mannite.  Like  mannite,  when  boiled  with  hydriodic  acid  it 
yields  secondary  hexyl  iodide, 


Sorbite,  C6H8(OH)6  +  jH2O.  —  Ordinary  sorbite  occurs  in 
the  berries  of  the  mountain  ash,  sorb  apple,  and  other  fruits, 
as  plums,  cherries,  apples,  etc.  It  is  formed  by  reduction  of 
glucose,  and  also  together  with  mannite  by  the  reduction  of 
fructose.  This  variety  is  known  as  dextro-sorbite,  because  it 
is  formed  from  glucose,  which  is  dextro-rotatory.  Levo-sorbite 
is  also  known,  having  been  obtained  by  the  reduction  of  levo- 
gulose.  _ 

There  are  no  hexa-basic  acids  known  belonging  to  this  series. 


HEPT-ACID  ALCOHOLS,  ETC. 

Perseite,  C7H9(OH)7,  occurs  in  the  fruit  and  leaves  of 
Laurus  persea,  and  has  been  made  artificially  from  dextro- 
mannose,  by  treating  it  with  hydrocyanic  acid,  converting  the 
nitril  thus  formed  into  the  corresponding  acid,  and  reducing 
this  acid.  It  is  also  called  dextro-mannoheptite.  By  similar 
reactions  an  oct-acid  and  an  alcohol  with  nine  hydroxyls  have 
been  made  from  glucose. 


CHAPTER  X 
MIXED  COMPOUNDS  —  DERIVATIVES  OF  THE  PARAFFINS 

UNDER  this  head  are  included  compounds  that  belong  at  the 
same  time  to  two  or  more  of  the  chief  classes  already  studied. 
Thus,  there  are  substances  which  are  at  the  same  time  alcohols 
and  acids.  There  are  others  which  are  at  the  same  time  alco- 
hols and  aldehydes,  alcohols  and  ketones,  acids  and  ketones, 
etc.  Fortunately,  for  our  purpose,  the  number  of  compounds 
of  this  kind  actually  known  is  comparatively  small,  though 
among  them  are  many  of  the  most  important  natural  com- 
pounds of  carbon.  The  first  class  that  presents  itself  is  that 
of  the  alcohol  acids  or  acid  alcohols;  that  is,  substances  that 
combine  within  themselves  the  properties  of  both  alcohol  and 
acid.  They  are  commonly  called  oxy  -acids  or  hydroxy-adds. 

HYDROXY-ACIDS,  CnH2ll03 

These  acids  may  be  regarded  either  as  monobasic  acids  into 
which  one  alcoholic  hydroxyl  has  been  introduced,  Or  as  mon- 
acid  alcohols  into  which  one  carboxyl  has  been  introduced.  As 
their  acid  properties  are  more  prominent  than  the  alcoholic 
properties,  they  are  commonly  referred  to  the  acids.  Running 
parallel,  then,  to  the  series  of  fatty  acids,  we  may  look  for  a 
series  of  hydroxy-acids,  each  of  which  differs  from  the  corre- 
sponding fatty  acid  by  one  atom  of  oxygen,  or  by  containing 
one  hydroxyl  in  the  place  of  one  hydrogen,  thus  :  — 

Fatty  acids  Hydroxy-acids 

H.C02H  HO.C02H. 

CH.C0H 


C2H5.C02H 


etc.  etc. 

157 


158  DERIVATIVES   OF   THE   PARAFFINS 

The  first  member  of  the  series,  which  by  analogy  would  be 
called  hydroxy-formic  acid,  is  plainly  the  ordinary  hypotheti- 
cal carbonic  acid.  Although  its  relation  to  formic  acid  is 
the  same  as  that  of  the  next  member  of  the  series  to  acetic 
acid,  it  has  no  properties  in  common  with  the  alcohols;  but, 
owing  to  its  peculiar  structure,  it  is  a  dibasic  acid  which  the 
other  members  of  the  series  are  not.  Nevertheless,  it  may  be 
referred  to  here  for  the  sake  of  a  few  of  its  derivatives,  which 
are  somewhat  allied  to  those  of  the  hydroxy-acids  proper. 

Carbonic  acid,  H2CO3(cO<QHj  --  It  is   believed  that 

this  body  exists  in  solutions  of  carbon  dioxide  in  water.  All 
that  is  known  about  it  is  that  it  is  a  feeble  dibasic  acid,  and 
breaks  up  into  water  and  carbon  dioxide  whenever  it  is  set 
free  from  its  salts.  We  have  seen  that  this  instability  is 
generally  met  with  in  compounds  containing  two  hydroxyls  in 
combination  with  one  carbon  atom. 

Among  the  derivatives  of  carbonic  acid  that  should  be 
mentioned  here  are  the  ethereal  salts.  These  may  be  made  :  — 

1.  By  treating  silver  carbonate,  c,0  <  QAg,  with  the  iodides 
of  alcohol  radicals  ;  as,  for  example,  — 


2.    By  treating  the  alcohols  with  carbonyl  chloride,  COC12:  — 
COC12  +  2  C2H5OH  =  CO(OC2H5)2  +  2  HC1. 

Cl 

Ethyl  chlor-carbonate,  OC  <  X^i  TT  •  —  This  compound  is 

002x1.5 

made  by  treating  alcohol  with'  carbonyl  chloride  :  — 
COC12  +  C2H5OH  =  00  <  ®        +  HC1. 

UO2tl5 

It  may  be  regarded  as  the  ethyl  ester  of  mono-chlor-formio 
acid,  Cl.COOH;  and,  properly  speaking,  should  be  called  ethyl 
chlor-formate. 


ETHYL   CHLOR-CARBONATE  1»59 

Carbon  bisulphide  acts  like  carbon  dioxide  towards  alka- 
lies and  alcohols,  and  yields  a  number  of  ether  acids  and 
ethereal  salts  containing  sulphur.  Thus,  when  carbon  bisul- 
phide is  added  to  a  solution  of  caustic  potash  in  alcohol,  a 

potassium  salt  of  the  formula  SC<gK2    5  is  formed.     This  is 

called  potassium  xanthogenate.  Free  xanthogenic  acid  is  very 
unstable,  breaking  up  into  alcohol  and  carbon  bisulphide. 
The  formation  of  the  salt  is  represented  by  the  following 
equation :  — 

OP  TT 
CS2  +  KOH  +  C2H5OH  =  SC  <  ^    5  +  H20. 

olv 

A  similar  salt  made  from  ordinary  amyl  alcohol  has  been  used 
for  the  purpose  of  destroying  phylloxera,  the  insect  which  is  so 
destructive  to  grape-vines,  particularly  in  the  wine  districts  of 
France. 

General  methods  for  the  preparation  of  hydroxy-acids.  The 
methods  available  for  making  the  hydroxy-acids  are  modifica- 
tions of  those  used  for  making  alcohols  and  acids. 

Starting  with  a  mon-acid  alcohol,  a  hydroxy-acid  can  be 
made  by  the  same  methods  that  were  used  in  making  an  acid 
from  a  hydrocarbon.  Suppose,  for  example,  that  it  is  desired 
to  make  acetic  acid  from  marsh  gas.  The  reactions  that  may 
be  used  are:  (1)  the  preparation  of  a  halogen  derivative; 
(2)  conversion  of  the  halogen  derivative  into  the  cyanogen 
derivative ;  and  (3)  conversion  of  the  cyanogen  derivative  into 
the  acid.  The  results  of  these  operations  are  described  by 
saying  that  carboxyl  has  been  introduced.  By  similar  opera- 
tions carboxyl  can  be  introduced  into  methyl  alcohol,  and  the 
product  is  hydroxy-acetic  acid. 

It  is,  however,  generally  better  to  start  with  an  acid,  and 
introduce  hydroxyl.  This  can  be  done  in  several  ways  :  — 

1.  By  treating  a  halogen  derivative  of  an  acid  with  water  or 
silver  hydroxide :  — 


160  DERIVATIVES   OF   THE  PARAFFINS 

CH°  <  S>2H  +  HHO  =  OH<<  C02H  +  HBr' 

Brom-acetic  acid 

2.    By  treating  an  amino  derivative  of  an  acid  with  nitrous 
acid  (see  page  100)  :  — 


CH2  <          .  +  HN02  =  CH2  <        H  +  K2  +  H20. 

Amino-acetic  acid 

3.   By  treating  a  salt  of  a  sulphonic-acid  derivative  of  an  acid 
with  caustic  potash  :  — 


Sulpho-acetic  acid 

The  first  two  of  these  reactions  have  been  described  and 
mentioned  as  affording  methods  for  the  introduction  of  hy- 
droxyl  into  hydrocarbons.  It  will  be  seen  that  the  only  dif- 
ference between  the  reactions  used  in  making  alcohols  and 
those  used  in  making  hydroxy-acids  is  that  in  one  case  we 
start  with  the  hydrocarbons,  while  in  the  other  we  start  with 
the  acids. 

Glycolic  acid,  hydroxy-acetic  acid,  oxy-acetic    acid, 

ethanolic   acid,    C2H4O3(CH2<  2?  „.).  —  Glycolic    acid    is 

\  OUsxi/ 

found  in  nature  in  unripe  grapes,  and  in  the  leaves  of  the  wild 
grape  (Ampelopsis  hederacea). 

It  can  be  made  from  glycocoll,  which  is  amino-acetic  acid  (see 
reaction  2,  above),  from  brom-  or  chlor-acetic  acid  and  water 
(see  reaction  1,  above),  and  by  the  oxidation  of  glycol:  — 

CH2OH  C02H 

I  +02=  |  +H20. 

CH2OH  CH2OH 

Glycol  Glycolic  acid 

This  results  in  transforming  one  of  the  primary  alcohol  groups, 
CH2OH,  contained  in  glycol,  into  carboxyl.     (What  would  be 


GLYCOLIC   ACID,   ETC.  161 

formed  by  conversion  of  both  the  primary  alcohol  groups  of 
glycol  into  carboxyl?)  It  can  also  be  made  by  careful  oxida- 
tion of  ethyl  alcohol  with  nitric  acid.  For  this  purpose  a 
mixture  of  alcohol  and  nitric  acid  is  allowed  to  stand  until  no 
further  action  takes  place. 

Gly  colic,  acid  forms  crystals  that  are  easily  soluble  in  water, 
alcohol,  and  ether. 

As  an  acid,  gly  colic  acid  forms  a  series  of  salts  with  metals, 
and  ethereal  salts  with  alcohol  radicals.  The  latter,  of  which 
ethyl  glycolate  may  be  taken  as  an  example,  can  be  made  by 
means  of  one  of  the  reactions  usually  employed  for  making 
ethereal  salts  ;  for  example,  by  treating  silver  glycolate  with 
ethyl  iodide:  — 


In  this  reaction,  as  well  as  in  the  formation  of  salts  of  glycolic 
acid,  the  alcoholic  hydroxyl  remains  unchanged. 

As  an  alcohol,  glycolic  acid  forms  ethers  of  which  ethyl- 

C\C^  TT 

glycolic  add,  CH2<C02H5,  may  serve  as  an  example.     It  will  be 

seen  that  this  is  isomeric  with  ethyl  glycolate.  But  while  the 
latter  has  alcoholic  properties,  the  former  has  acid  properties. 
Ethyl  glycolate  is  a  liquid  that  boils  at  160°.  Ethyl-glycolic 
acid  is  a  liquid  that  boils  at  206°  to  207°.  Finally,  as  an 
alcohol,  glycolic  acid  forms  ethereal  salts,  of  which  acetyl- 
glycolic  acid  may  serve  as  an  example.  This  is  glycolic  acid 
in  which  the  hydrogen  of  the  hydroxyl  is  replaced  by  acetyl, 

O  P  TT  O 

CH2<CQ  *H  3   .    As  will  be  seen,  this  bears  the  same  relation  to 

glycolic  acid  and  acetic  acid  that  ethyl  acetate,  C2H5.O.C2H30, 
bears  to  alcohol  and  acetic  acid. 

Glycolic  acid  and  some  of  the  other  acids  of  the  series  lose 
water  when  heated,  and  yield  anhydrides.     Thus  glycolic  anhy- 

H2COH 

dride,       \  ,  is   formed   when   glycolic   acid  is 

00  -  OCH2.COOH 


162  DERIVATIVES    OP    THE   PARAFFINS 

heated  to  100°.  This  substance  is  plainly  an  ester,  an  alcohol, 
and  an  acid. 

When  glycolic  acid  is  heated  to  250°-280°  it  yields  glycolide, 
which  is  believed  to  be  derived  from  the  acid  as  represented  in 
this  equation :  — 

OH  CH2-0-CO 

2CH2<  =   |  |       +2H20. 

CO   -0-CH2 

It  is  a  double  ester  resulting  from  the  interaction  of  the 
alcoholic  hydroxyl  of  each  molecule  of  the  glycolic  acid  with 
the  carboxyl  of  the  other. 

Glycolide  is  insoluble  in  cold  water.  When  boiled  for 
a  long  time  with  water,  glycolide  is  converted  into  glycolic 
acid. 

Lactic  acids,  hydroxy-propionic  acids,  oxy-propionic 
acids,  CsHeOs^H^QQ  -rrj.  —  In  speaking  of  propionic 

acid,  it  was  pointed  out  that  two  series  of  substitution-products 
of  the  acid  are  known,  which  are  designated  as  the  a-  and  (3- 
series.  Accordingly  we  should  expect  to  find  two  hydroxy- 
propionic  acids,  the  a-  and  the  /3-acid.  Two  lactic  acids  have 
been  known  for  a  long  time.  One  of  these  is  ordinary  lactic 
acid;  the  other  a  variety  that  is  found  in  meat,  and  hence 
called  sarco-lactic  acid.  But,  strange  to  say,  a  thorough  in- 
vestigation of  these  two  acids  has  proved  that  both  must  be 
represented  by  the  same  structural  formula,  as  both  conduct 
themselves  in  exactly  the  same  way  towards  reagents.  Further, 
two  other  hydroxy-propionic  acids  are  certainly  known.  The 
facts  then  are  these:  four  acids  are  known,  all  of  which  are 
hydroxy-propionic  acids.  Our  ordinary  theory  enables  us  to 
foretell  the  existence  of  only  two.  Before  discussing  this 
discrepancy  let  us  learn  something  of  the  acids  themselves. 


LACTIC   ACIDS  163 

1.   Lactic  acid,  inactive  ethylidene-lactic  acid,  a-hy- 

OH 
droxy-propionic    acid,    CH3.CH  <  CQ  H.  —  Lactic    acid   is 

made  by  the  fermentation  of  sugar,  as  has  already  been  de- 
scribed under  Butyric  Acid  (which  see).  The  process  is  car- 
ried out  best  by  dissolving  cane  sugar  and  a  little  tartaric  acid 
iii  water;  then  adding  putrid  cheese,  milk,  and  zinc  carbonate, 
the  object  of  which  is  to  prevent  the  solution  from  becoming 
acid,  as  the  presence  of  free  acid  is  fatal  to  the  ferment.  Lac- 
tic acid  can  also  be  made  by  fermentation  of  sugar  of  milk, 
and  is  hence  contained  in  sour  milk  ;  by  boiling  a-chlor-pro- 
pionic  acid  with  alkalies,  — 

CH3.CH  <  +  KOH  =  CH3.CH< 


and  by  treating  alanine  (a-amino-propionic  acid)  with  nitrous 
acid,  — 


CH3.CH  <          .  +  HN02=CH3.CH  <        H  +  N2  +  H2O. 

Lactic  acid  is  a  thick  liquid  that  mixes  with  water  and  with 
alcohol  in  all  proportions. 

When  commercial  lactic  acid  of  specific  gravity  1.21  is  dis- 
tilled under  much  diminished  pressure  (1  mm.  of  mercury)  and 
the  distillate  allowed  to  stand  in  a  freezing-mixture  for  a  time, 
it  takes  the  form  of  crystals  that  melt  at  17°.5-18°. 

Treated  with  hydriodic  acid,  it  is  reduced  to  propionic  acid, 

O-JT 
CH3.CH  <  0Q  H  +  2  HI  =  CH3.CH2.C02H  +  H20  4-  1* 

2.   Sarco-lactic     acid,    dextro-ethylidene-lactic     acid, 

OH 
CH3CH<  pjQ  XT'  —  This  acid  occurs  in  the  liquids  expressed 

from  meat.     It  is  therefore  contained  in  "extract  of  meat," 
and  can  be  obtained  most  readily  from  this  source. 

Its  properties  are,  for  the  most  part,  like  those  of  inactive 


164  DERIVATIVES   OF  THE  PARAFFINS 

lactic  acid,  and  its  conduct  towards  reagents  is  in  all  respects 
the  same.  Its  salts  are  somewhat  more  easily  soluble  than 
those  of  ordinary  inactive  lactic  acid.  The  chief  difference 
between  the  two  is  observed  in  the  action  towards  polarized 
light.  Dextro-lactic  acid  turns  the  plane  of  polarization  to  the 
right.  Its  salts  are  all  levo-rotatory.  On  the  other  hand, 
neither  inactive  lactic  acid  nor  its  salts  exert  any  action  upon 
polarized  light.1 

OTT 

3.  Levo-lactio  acid,  CH3.CH<QQ  jj  —  A    third  variety 

of  ethylidene-lactic  acid,  that  turns  the  plane  of  polarization 
to  the  left,  is  formed  from  cane  sugar  by  the  action  of  a  certain 
bacillus  found  in  a  spring-water.  By  fractional  crystallization 
of  the  strychnine  salt  of  ordinary  inactive  lactic  acid  two  kinds 
of  crystals  are  obtained.  The  acid  separated  from  one  kind  is 
sarco-lactic,  or  dextro-lactic,  acid;  while  that  separated  from 
the  other  kind  is  levo-lactic  acid.  This  method  of  splitting 
the  inactive  acid  into  the  two  active  varieties  is  applicable  to 
many  other  similar  cases.  The  relations  between  these  three 
acids  are  of  the  same  kind  as  those  existing  between  the  three 
varieties  of  tartaric  acid  (which  see). 

4.  Hydracrylic  acid,  1  CH2OH 
£-hydroxy-propionic  acid,  J  CH2.CO2H 

Hydracrylic  acid  is  made  by  boiling  /?-iodo-propionic  acid  with 
water  or  silver  oxide  and  water:  — 

CH2I  CH2.OH 

|  +HHO  =  |  +  HI. 

CH2.C02H 


CH2 
It  is  made  also  by  starting  with  ethylene,  ||     .     When  this 

CH2 
hydrocarbon  is  treated  with  hypochlorous  acid,  HOC1,  it  is  con- 

1  See  active  and  inactive  amyl  alcohols,  p.  127. 


HYDR ACRYLIC   ACID  165 

CH2C1 
verted    into    ethylene-chlorhydrine,  |  (which,    see).     By 

CH2OH 
replacing  the  chlorine  with  cyanogen,  and  boiling  the  cyan- 

CH2CN 
hydrine,    |          ,  thus  obtained,  with  an  alkali,  hydracrylic  acid 

CH2OH 
is  obtained. 

These  reactions  clearly  show  that  hydracrylic  acid  is  an 
ethylene  compound,  and,  as  it  is  made  from  /?-iodo-propionic 
acid  by  replacing  the  iodine  with  hydroxyl,  it  follows  further 
that  the  /^-substitution-products  of  propionic  acid  are  ethylene 
products,  and  that  the  a-products  are  ethylidene  products  (see 
p.  132). 

Hydracrylic  acid  is  a  syrup.  Its  salts  differ  markedly  from 
those  of  the  inactive  and  active  lactic  acids.  When  heated,  it 
loses  water  and  is  transformed  into  acrylic  acid,  CH2:CH.C02H 
(which  see). 

The  difference  in  conduct  between  ethylidene-lactic  acid  and 
ethylene-lactic  acid,  when  heated,  is  interesting  and  suggestive. 
When  ethylidene-lactic  acid  is  heated,  both  its  acid  and  alco- 
holic properties  are  destroyed,  both  the  alcoholic  and  acid 
hydroxyls  taking  part  in  the  reaction.  Whereas,  when 
ethylene-lactic  acid  is  heated,  only  the  alcoholic  properties  are 
destroyed,  the  carboxyl  remaining  intact. 

There  are  then  more  hydroxy-propionic  acids  known  than  our 
theory  of  linkage  in  its  simplest  form  can  account  for.  Other 
cases  of  this  kind  are  known,  and  one  very  marked  and 
especially  interesting  one  will  be  taken  up  when  tartaric  acid 
is  treated  of.  It  will  be  shown  that  just  as  there  are  two 
active  lactic  acids  and  an  inactive  one,  so  there  are  two  active 
tartaric  acids  and  an  inactive  one,  which  conduct  themselves  in 
the  same  way  towards  reagents,  and  must  hence  be  represented 
by  the  same  structural  formula. 

We  have  here  to  deal  with  a  new  kind  of  isomerism.  Com- 
pounds may  conduct  themselves  chemically  in  the  same  way, 


166 


DERIVATIVES    OF   THE   PARAFFINS 


and  yet  differ  in  some  of  their  physical  properties,  as  in  their 
action  towards  polarized  light.  To  distinguish  this  kind  of 
isomerism  from  ordinary  chemical  isomerism  it  has  been  called 
physical  isomerism. 

An  ingenious  hypothesis  has  been  put  forward  by  way  of 
explanation  of  that  particular  kind  of  physical  isomerism  which 
shows  itself  in  the  action  of  compounds  upon  polarized  light. 
It  must  be  remembered  that  our  ordinary  formulas  ha.ve  nothing 
whatever  to  do  with  the  relations  of  the  atoms  arid  groups  in 
space.  They  indicate  chemical  relations  that  are  discovered  by 
a  study  of  chemical  reactions. 

Let  us  suppose  that  in  a  carbon  compound  one  carbon  atom 
is  situated  at  the  centre  of  a  tetrahedron,  and  that  the  four 
atoms  or  groups  which  it  holds  in  combination  are  at  the  angles 
of  the  tetrahedron,  as  represented  in  Fig.  10. 

If  these  groups  are  all  different  in  kind,  and  only  in  this 
case,  it  is  possible  to  arrange  them  in  two  ways  with  reference 
to  the  carbon  atom.  The  difference  between  the  two  arrange- 


Fig.  10. 


Fig.  11. 


ments  is  that  which  is  observed  between  either  one  and  its 
reflection  in  a  mirror.  Imperfectly  the  second  arrangement 
is  shown  in  Fig.  II.1 

A  carbon  atom,  in  combination  with  four  different  kinds  of 
atoms  or  groups,  is  called  an  asymmetrical  carbon  atom.  When- 
ever, therefore,  a  compound  contains  an  asymmetrical  carbon 
atom,  there  are  two  possible  arrangements  of  its  parts  in  space 


1  This  can  be  made  clear  only  by  means  of  models.    These  can  easily  be  made  of  stout 
wire  and  wooden  balls. 


ISETHIONIC   ACID  167 

which  correspond  to  the  two  complementary  tetrahedrons,  viz., 
the  right-handed  and  the  left-handed  tetrahedron. 

In  ethylidene  lactic  acid  there  is  an  asymmetrical  carbon  atom, 
as  shown  by  the  ordinary  formula,  which  may  be  written  thus  : 
H 

CH3  -  C  —  OH,  the  central  carbon  atom  appearing  in  combination 
I 
C02H 

with  (1)  hydrogen,  (2)  hydroxyl,  (3)  carboxyl,  and  (4)  methyl. 
Hence,  according  to  the  hypothesis  just  stated,  there  ought  to 
be  two  possible  arrangements  of  the  constituents  of  this  com- 
pound, one  corresponding  to  the  right-handed  tetrahedron,  the 
other  to  the  left-handed  tetrahedron.  Both  would  be  ethylidene- 
lactic  adds.  The  inactive  variety  is  formed  by  the  combination 
of  the  two  active  varieties,  and  must,  therefore,  have  a  greater 
molecular  weight  than  these. 

The  branch  of  chemistry  that  has  to  deal  with  the  kind 
of  isomerism  just  referred  to  is  called  stereo-chemistry.  The 
phenomena  of  stereo-chemistry  have  been  the  subject  of  exten- 
sive investigation,  and  the  facts  established  furnish  a  strong 
foundation  for  the  theory  briefly  expounded  above. 

Hydroxy-sulphonic  acids.  —  It  has  been  pointed  out  that 
the  sulphonic  acids  and  the  carbonic  acids  are  analogous  :  that, 
for  example,  methyl-sulphonic  acid,  CH3.S03II,  is  analogous  to 
methyl-carbonic  or  acetic  acid,  CH3.C02H.  Now,  just  as  the 
hydroxy-acids  already  treated  of  are  derived  from  the  carbonic 
acids  by  the  introduction  of  hydroxyl,  so  there  are  hydroxy- 
acids  derived  in  a  similar  way  from  the  sulphonic  acids. 
Only  one  such  acid  is  well  known.  It  is  — 

OH 

Isethionic  acid,  C,H4<  ,  also  called  p-hydroxy-ethyl- 


sulphonic  acid.  In  composition  it  is  analogous  to  the  hydroxy- 
propionic  acids.  It  is  prepared  by  passing  sulphur  trioxide  into 
well  cooled  alcohol  or  ether  and  boiling  the  product  with 


168  DERIVATIVES   OF  THE  PARAFFINS 

water;  and  also  by  treating  taurine  (which  see)  with  nitrons 
acid :  — 

CH2.NH2  CH2OH 

I  +HN02=  |  +  11,0  +  1*,. 

CH2.S03H  CH2.S03H 

LACTONES 

The  monohydroxy-monobasic  acids  of  the  paraffin  series  are 
designated  as  a-,  (3-,  y-,  8-,  etc.,  acids,  according  to  the  position 
of  the  hydroxyl  with  reference  to  the  carboxyl.  When  the 
hydroxyl  is  united  with  the  carbon  atom  with  which  the  car- 
boxyl is  united  the  product  is  called  an  a-hydroxy-acid.  When 
the  hydroxyl  is  united  with  the  next  carbon  atom  in  the  chain 
the  product  is  called  a  /?-hydroxy-acid,  etc.  The  following 
examples  will  make  this  clear :  — 

Acids  of  the  formulas 

CH2(OH).C02H,  CH3.CH(OH).C02H,  CH3.CH2.CH(OH).C02H 
are  a-hydroxy-acids. 
Acids  of  the  formula 

CH2(OH).CH2.C02H,  CH3.CH(OH).CH2.C02H, 
CH3.CH2.CH(OH).CH2.C02H  are  /ttiydroxy-acids. 
Acids  of  the  formulas 

CH2(OH).CH2.CH2.C02H,  etc.,  are  y-hydroxy-acids. 
Similarly  an  acid  of  the  formula 
CH2(OH).CH2.CH2.CH2.C02H  is  called  a  8-hydroxy-acid. 

The  y-  and  8-acids  differ  from  the  others  in  this  respect  that 
they  lose  the  elements  of  water  when  set  free  from  their  salts. 
Thus,  when  a  salt  of  y-hydroxy-butyric  acid  in  solution  is 
treated  with  a  mineral  acid,  a  neutral  compound  is  precipitated 
and  not  the  acid  corresponding  to  the  salt.  The  compound 
thus  formed  is  called  a  lactone.  The  reaction  between  sodium 


HYDROXY-ACIDS  169 

y-hydroxy-butyrate  and  hydrochloric  acid  is  represented  by  the 
following  equation :  — 

CH2(OH).CH2.CH2.C02Na  +  HCl 
=  CH2.CH2.CH2.CO  +  NaCl  +  H20. 

The  change  from  the  free  acid  to  the  lactone  may  be  repre- 
sented thus : — 


CH2.CH2(OH) 

~+H20. 
CH2.CO.OH       CH2.CO  / 

The  reaction  is  similar  to  that  which  takes  place  when  sue- 
cinic  acid  is  heated :  — 

CH2.CO.OH      CH2.COV 

I  =    |  >0  +  H20. 

CH2.CO.OH      CH2.C(K 

The  product  in  this  case  is  an  anhydride.  The  lactones  may 
be  defined  as  anhydrides  of  hydroxy-acids.  They  are  neutral, 
but  they  form  the  salts  of  the  corresponding  hydroxy-acids 
when  they  are  boiled  for  some  time  with  bases  in  solution. 

HYDROXY-ACIDS,  CnH2n04 

The  acids  just  treated  of  are  called  monohydroxy-monobasic 
acids.  Similarly,  there  are  dihydroxy-monobasic  acids,  which 
are  derived  from  the  monohydroxy-acids  by  the  introduction  of 

PC)  TT 

a  second  hydroxyl.     Thus,  if  into  lactic  acid,  CH3.CH  <       2    , 

a  hydroxyl  should  be  introduced  into  the  methyl,  the  product 

CH2.OH 

I 
would  have  the   formula  CH.OH.     This    is    the   best-known 

I 

C02H 

dihydroxy-monobasic  acid  of  the  paraffin  series. 


170  DERIVATIVES   OF   THE   PARAFFINS 


Glyceric  acid,  propandiolic  acid,  C3H6O4 


CH.OH 


CHOH 
CO,H 


This  acid  has  been  referred  to  as  the  first  product  of  the  oxida- 
tion of  glycerol.  It  is  prepared  by  allowing  glycerol  and  nitric 
acid  to  stand  together  at  the  ordinary  temperature  for  some 
time,  and  then  heating  on  the  water-bath.  It  can  also  be  made 
by  treating  /?-chlor-lactic  acid  with  water. 

An  optically  active  variety  of  glyceric  acid  has  been  obtained 
from  the  inactive  variety.  It  will  be  seen  that  the  acid  con- 
tains an  asymmetric  atom. 

Glyceric  acid  is  a  thick  syrup  that  mixes  with  water  and 
alcohol.  When  treated  with  very  concentrated  hydriodic  acid, 
it  is  converted  into  /?-iodo-propionic  acid.  This  conversion 
involves  two  reactions:  — 

CH2OH  CH2I 

I  I 

(1)  CHOH  +  HI     =  CHOH  +  H20,  and 

I  I 

C02H  C02H 

CH2I  CH2I 

•  I  I 

(2)  CHOH  +  2  HI  =  CH2     -f  H20  +  21. 

I  I 

C02H  C02H 

OTHER  HYDROXY-MONOBASIC  ACIDS 

Just  as  by  oxidation  of  the  tri-acid  alcohol,  glycerol,  a  dihy- 
droxy-monobasic  acid  can  be  formed,  so  by  oxidation  of  the 
tetr-acid  alcohol,  erythrol,  a  trihydroxy-monobasic  acid  can  be 
formed.  This  is  erythritic  add.  Its  relation  to  erythrol  is 
like  that  of  glyceric  acid  to  glycerol:  — 


MANNONIC    ACIDS  171 

CH2OH  CH2OH  CH2OH  CH2OH 

I  1  I  I 

CHOH  CHOH  CHOH  CHOH 

I  I  I  I 

CH2OH  C02H  CHOH  CHOH 

Glycerol  Glyceric  acid  |  | 

CH2OH  C02H 

Erythrol  Erythritic  acid 

Similarly  from  the  pent-acid  alcohols  tetrahydroxy-mono- 
basic  acids,  and  from  the  hex-acid  alcohols,  pentahydroxy- 
monobasic  acids  can  be  made.  The  latter  are  of  special 
importance  on  account  of  their  connection  with  the  sugars. 

Mannonic  acids,  C6H12O7(C3H6(OH)5CO2H). — Three  acids 
are  included  in  this  group.  They  are  the  dextro,  the  levo, 
and  the  inactive  varieties,  or  d-1  mannonic,  I-1  mannonic, 
i-lmannonic  acids.  They  are  related  to  the  three  mannites 
and  the  three  mannoses.  As  will  be  shown  further  on,  the 
mannoses  are  pentahydroxy-aldehydes  and  the  relations  here 
referred  to  are  represented  by  the  following  formulas  :  — 

CH2OH  CHoOH  CH2OH 

I  I  I 

CHOH  CHOH  CHOH 

I  I  I 

CHOH  CHOH  CHOH 

I  I  I 

CHOH  CHOH  CHOH 

I  I  I 

CHOH  CHOH  CHOH 

I  I  I 

CH2OH  COH  C02H 

Mannite  Mannose  Mannonic  acid 

The  difference  between  the  three  mannonic  acids  is  of  the 
same  kind  as  that  between  the  three  lactic  acids.  The  dextro 
and  levo  varieties  are  complementary  forms,  while  the  inactive 

1  Instead  of  using  the  prefixes  dextro-  and  levo-,  and  the  word  inactive,  it  is  customary 
to  use  the  letters  d-,  1-,  and  i-,  as  they  are  here  used. 


172  DERIVATIVES   OF   THE  PARAFFINS 

variety  is  formed  by  a  combination  of  the  dextro  and  levo 
varieties. 

Gluconic  acids,  C6H12O?[C5H6(OH)5CO|HJ.  — The  gin- 
conic  acids  are  related  to  the  three  glucoses  in  the  same  way 
that  the  mannonic  acids  are  related  to  the  mannoses.  Dextro- 
gluconic  acid  is  formed  by  the  oxidation  of  glucose  and  of  cane 
sugar.  When  heated  with  quinoline  to  140°,  it  is  partly  con- 
verted into  cZ-mannonic  acid.  Similarly  d-mannonic  acid  is 
partly  converted  into  d-gluconic  acid  by  the  same  process. 
Three  Gulonic  acids  and  three  Galactonic  acids  of  the 
same  composition  and  structure  as  the  mannonic  and  the  glu- 
conic acids  are  also  known. 

The  existence  of  so  many  acids  of  the  formula 

C5H6(OH)5C02H 

is  due  to  the  fact  that  a  substance  made  up  as  represented  in 
the  formula 

CH2OH 

I 

CHOH 

I 

CHOH 

I 

CHOH 

I 

CHOH 

I 

C02H 

contains  four  asymmetric  carbon  atoms.  The  total  number 
of  isomers  possible,  according  to  the  theory,  is  sixteen  —  eight 
dextro  and  eight  levo,  besides  eight  racemic. 

HYDROXY-ACIDS,  CnH2n_204 

The  acids  included  under  this  head  are  monohydroxy-dibasic 
adds.  They  bear  the  same  relation  to  the  dibasic  acids  of  the 
oxalic  acid  series  that  the  simplest  hydroxy-acids  bear  to  the 


HYDROXY-SUCCINIC    ACIDS  173 

members  of  the  formic  acid  series.  The  principal  members  of 
this  series,  and  the  only  ones  that  will  be  treated  of,  are 
tartronic  acid  and  malic  acid. 

Tartronic   acid,    C3H4O3(cH(OH)<CO2HY_This  ac^ 

V  CO2H' 

is  prepared  by  an  indirect  method  from  tartaric  acid.  It  can 
be  made,  — 

(1)  By  boiling  brom-malonic  acid  with  silver  oxide   and 
water  :  — 

cHBr<co:S+  Ag°H  =cH(°H)<co2l+  AgBr; 

(2)  By  treating  brom-cyan-acetic  acid  with  caustic  potash:  — 

PAT 

CHBr<  £:  w+2  KOH  +  H20 

ou2ii 

=  CH(OH)  <  ^  +  NH3  +  KBr. 

OU2rl 

Tartronic  acid  is  a  solid  that  crystallizes  in  prisms.  It  is 
easily  soluble  in  water,  alcohol,  and  ether.  The  anhydrous 
acid  melts  at  185—187°  with  evolution  of  carbon  dioxide  and 
water,  and  forms  glycolide  (which  see)  :  —  • 


(1) 

Glycolic  acid 
OTT  CH2-0-CO 

(2)  2CH2<  =  |  |       +  2H20. 


Glycolide 

NOTE  FOR  STUDENT.  —  Compare  reaction  (1)  with  that  which  takes 
place  when  iso-succinic  acid  is  heated,  and  note  the  analogy. 

Hydroxy-succinic  acids,    aH,oJc2H3(OH)<C°2H^  __ 

5V  co2Hy 

Three   hydroxy-succinic   acids    are  known,  the  principal  one 
being  ordinary  malic  acid. 


174  DERIVATIVES   OF  THE  PARAFFINS 

/CH(OH).CO2H\ 

Malic  acid,  C4H6O5(  I  ).  —  This  acid  is  very 

\CH2  .CO2H         / 

widely  distributed  in  the  vegetable  kingdom,  as  in  the  berries 
of  the  mountain  ash,  in  apples,  cherries,  etc. 

It  is  best  prepared  from  the  berries  of  the  mountain  ash 
which  have  not  quite  reached  ripeness.  The  berries  are  pressed 
and  boiled  with  milk  of  lime.  The  acid  passes  into  solution  as 
the  calcium  salt,  and  this  is  purified  by  crystallization. 

It  can  also  be  made  by  treating  aspartic  acid,  which  is  ammo- 

(T)     TT 

succinic  acid,  C2H3(NH2)<C02H,  with  nitrous  acid,  and  by  treat- 

ing tartaric  acid  with  hydriodic  acid.  This  latter  reaction  will 
be  explained  when  tartaric  acid  is  treated  of.  Tartaric  and 
malic  acids  are  closely  related  to  .each  other,  and  both  are 
related  to  succinic  acid,  as  will  appear  from  the  reactions. 

Malic  acid  is  a  solid  substance  that  crystallizes  with  diffi- 
culty. It  is  very  easily  soluble  in  water  and  in  alcohol.  Its 
solutions  turn  the  plane  of  polarization  to  the  right  or  to  the  left, 
according  to  the  concentration. 

When  heated  it  loses  water  and  yields  fumaric  acid  and 
maleic  anhydride  (which  see).  Fumaric  and  maleic  acids 
are  isomeric,  and  both  are  represented  by  the  formula 

C2H2<C02H.  The  reaction  mentioned  is  represented  by  the 
following  equation:  — 


M*  ac,d 

NOTE  FOR  STUDENT.  —  Compare  this  reaction   with  that  which  takes 
place  when  hydracrylic  acid  is  heated,  and  note  the  analogy. 

When  treated  with  hydriodic  acid,  malic  acid  is  reduced  to 
succinic  acid. 

NOTE  FOR  STUDENT.  —  Compare    this  reaction  with    the    conduct  of 
lactic  and  gly  eerie  acids  when  treated  with  hydriodic  acid. 


INACTIVE   MALIC    ACID  175 

Treated  with  hydrobroinic  acid,  malic  acid  is  converted  into 
mono-brom-succinic  acid. 

The  reactions  just  described  show  clearly  that  malic  acid  is 
hydroxy-succinic  acid.  Nevertheless,  if  hydroxy-succinic  acid 
is  made  by  treating  brom-succinic  acid  with  silver  oxide  and 
water,  the  product  is  not  identical  with  ordinary  malic  acid, 
though  the  two  resemble  each  other  very  closely.  The  acid 
thus  obtained  is  :  — 


Inactive  malic  acid,  CsHXOHX  QQ'JJ-  ~~  Inactive  malic 
acid  can  be  made  not  only  by  the  method  first  mentioned,  but 
by  several  others,  which  indicate  that  the  relation  between  it 
and  succinic  acid  is  that  expressed  in  the  formula  given.  It, 
like  ordinary  malic  acid,  is  unquestionably  a  hydroxy-succinic 
acid,  and  both  are  derived  from  ordinary  succinic  acid. 

Other  reactions  for  the  preparation  of  inactive  malic  acid 
are  :  — 

(1)  By  treating  dichlor-propionic  acid  with  potassium  cyanide, 
and  boiling  the  product  with  caustic  potash  :  — 

CH2C1.CHC1.C02H  +  KCN 

CH2CN 

=    I  +KC1; 

CHC1.C02H 


and         |  -f2KOH 

CHC1.C02H 

CH2.C02K 
=   | 

CH(OH).C02H 

(2)  By  heating  fumaric  acid  with  water  :  — 


C2H2  <  +  H20  =  C2H3(OH)<  :  ;  and 

(3)  By  reducing  racemic  acid  with  hydriodic  acid.  Race- 
mic  acid  has  the  same  composition  as  tartaric  acid.  The  latter, 
when  treated  with  hydriodic  acid,  yields  active  malio  acid, 


176  DERIVATIVES    OF   THE   PARAFFINS 

The  properties  of  inactive  malic  acid  are  very  much  like 
those  of  active  malic  acid.  As  regards  their  chemical  conduct 
they  are  almost  identical.  The  principal  difference  between 
them  is  observed  in  their  conduct  towards  polarized  light. 
They  present  a  new  case  of  physical  isomerism  of  the  same 
kind  as  that  referred  to  in  connection  with  the  lactic  acids 
(which  see). 

Dextro-malic  acid.  —  Inactive  malic  acid  bears  the  same 
relation  to  two  active  acids  that  inactive  lactic  acid  bears  to  the 
two  active  varieties  of  that  acid.  When  the  cinchonine  salt  of 
inactive  malic  acid  is  subjected  to  fractional  crystallization,  two 
different  salts  are  obtained.  One  of  these  is  derived  from 
ordinary  levo-malic  add,  while  the  other  is  derived  from  the 
isomeric  dextro-malic  add. 

HYDBOXY-ACIDS,  CnH2n_206 

These  are  di-hydroxy-dibasic  adds.  The  chief  members  of 
the  group  are  mesoxalic  acid  and  the  different  modifications  of 
tartaric  acid. 

Mesoxalic    acid,    C3H4O6(c(OH)2<  °°2^).  — This  acid 

\  OU^xl/ 

is  obtained  by  indirect  and  rather  complicated  reactions  from 
uric  acid  (which  see).  It  has  been  made  also  by  boiling  di- 
brom-malonic  acid  with  baryta-water  and  by  oxidizing  glycerol 
(see  p.  152). 

NOTE  FOR  STUDENT.  —  Explain  this  reaction. 

The  acid  forms  deliquescent  needles.  When  its  aqueous 
solution  is  boiled,  it  loses  carbon  dioxide,  and  glyoxylic  acid, 
a  half  aldehyde  of  oxalic  acid,  is  formed :  — 

PO  l-T      CHO 

I         +C02  +  H20. 
C02H 

Glyoxylic  acid 


DI-HYDKOXY-SUCCINIC   ACIDS  177 

Mesoxalic  acid  affords  an  example  of  a  rare  condition,  viz., 
the  existence  of  a  compound  in  which  two  hydroxyls  are  in 
combination  with  one  and  the  same  carbon  atom.  This  same 
condition  exists  in  chloral  hydrate.  The  acid  readily  loses 
water  and  passes  over  into  the  form  CO(COOH)2. 


/ 
Di-hydroxy-succinic  acids,  C4H6O6(  C2H2(OH)2 


< 


CH(OH)  .  CO2H 

1.   Tartaric  acid,  I  •  —  Ordinary  tartaric  acid 

CH(OH)  .  CO2H 

occurs  widely  distributed  in  fruits,  sometimes  free,  sometimes 
in  the  form  of  the  potassium  or  calcium  salt  ;  as,  for  example, 
in  grapes,  berries  of  the  mountain  ash,  potatoes,  cucumbers, 
etc.,  etc. 

It  can  be  made  by  the  following  methods  :  — 

(1)  By  oxidizing  sugar  of  milk  with  nitric  acid  ; 

(2)  By   oxidizing   cane   sugar,   starch,  glucose,   and   other 
similar  substances. 

Tartaric  acid  is  prepared  from  "tartar,"  which  is  impure 
acid  potassium  tartrate.  When  grape  juice  ferments  this 
salt  is  deposited.  It  is  purified  by  crystallization,  converted 
into  the  calcium  salt  by  treating  it  with  chalk  and  calcium 
chloride,  and  the  salt  then  decomposed  by  means  of  sulphuric 
acid. 

The  acid  crystallizes  in  large  rnonoclinic  prisms,  which  are 
easily  soluble  in  water  and  in  alcohol.  It  melts  at  170°.  Its 
solution  turns  the  plane  of  polarization  to  the  right. 

Treated  with  hydriodic  acid,  tartaric  acid  yields,  first,  malic 
acid,  and  then  ordinary  succinic  acid  :  — 


(1) 


PO  TT 

C2Ha(OH)  <  Jjg  +  H20 

Malic  acid 


178  DERIVATIVES   OF   THE  PARAFFINS 

PO  TT 

(2)        C2H3(OH)  <+2HI 


Succinic  acid 

While  malic  acid  is  mono-hydroxy-succinic  acid,  ordinary 
tartaric  acid  is  di-hydroxy-succinic  acid.  But,  just  as  the 
malic  acid  prepared  from  mono-brom-succinic  acid  is  optically 
inactive,  and  therefore  different  from  the  natural,  active 
malic  acid,  so,  too,  the  tartaric  acid  prepared  from  di-brom-suc- 
cinic  acid  is  optically  inactive,  and  therefore  different  from 
ordinary  tartaric  acid.  The  relations  between  the  natural  and 
the  artificial  acids  will  be  more  fully  dealt  with  below. 

Tartrates.     Among  the  salts  the  following  may  be  mentioned  : 

Mono-potassium  tartrate,  KH.C4H406.  This  is  the  chief  con- 
stituent of  tartar.  In  pure  form,  as  used  in  medicine,  it  is 
known  as  cream  of  tartar. 

Sodium-potassium  tartrate,  KNa  .  C4H406  +  4  H20.  This  salt 
crystallizes  beautifully.  It  is  known  as  Rochelle  salt  or 
Seignette  salt.  Seidlitz  powders  consist  of  (1)  a  mixture  of 
Rochelle  salt  and  'sodium  bicarbonate,  and  (2)  tartaric  acid. 
These  are  dissolved  separately  and  then  brought  together,  when 
a  rapid  evolution  of  carbon  dioxide  takes  place. 

Calcium  tartrate,  Ca  .  C4H406  +  4  H20.  This  salt  occurs  in 
senna  leaves  and  in  grapes.  It  forms  a  crystalline,  powder  or 
rhombic  octahedrons  insoluble  in  water. 

Potassium-antimonyl  tartrate,  K(SbO)  .  C4H406  4-  £  H20.  This 
is  known  as  tartar  emetic.  It  is  prepared  by  digesting  anti- 
monic  oxide  with  mono-potassium  tartrate.  It  crystallizes  in 
rhombic  octahedrons.  It  loses  its  water  of  crystallization  at 
100°,  and  at  200°  to  220°  is  converted  into  an  antimony  potas- 
sium salt  of  the  formula  KSb  .  C4H206. 

2.  Racemic  acid,  (C4H6O6)2  •  2  H2O.  —  Kacemic  acid  occurs, 
together  with  tartaric  acid,  in  many  kinds  of  grapes,  and,  on 


RACEMIC  ACID  179 

recrystallizing  the  crude  tartar,  acid  potassium  racemate,  being 
more  soluble  than  the  tartrate,  remains  in  the  mother  liquors. 
Racemic  acid  is  formed  by  boiling  ordinary  tartaric  acid  with 
water,  or  with  hydrochloric  acid.  If  tartaric  acid  is  heated 
with  water  in  sealed  tubes  at  175°,  it  is  almost  completely 
transformed  into  racemic  acid.  It  is  formed  further  by  oxida- 
tion of  dulcite,  mannite,  cane  sugar,  gum,  etc.,  with  nitric  acid. 
It  is  formed,  together  with  a  third  variety  of  tartaric  acid  known 
as  inactive  tartaric  acid,  when  di-brom-succinic  acid  is  treated 
with  silver  oxide  and  water. 

Eacemic  acid  differs  from  tartaric  acid  in  many  ways.  It 
crystallizes  differently,  and  contains  water  of  crystallization. 
It  is  less  soluble  than  tartaric  acid.  It  produces  precipitates  in 
solutions  of  lime  salts,  while  tartaric  acid  does  not.  JZacemic 
acid  is  optically  inactive,  while  tartaric  acid  is  dextro-rotatory. 
On  the  other  hand,  racemic  and  tartaric  acids  conduct  them- 
selves towards  most  reagents  exactly  alike. 

The  relations  between  racemic  and  tartaric  acid  are  the  same 
as  those  which  have  already  been  referred  to  as  existing  between 
inactive  malic  acid  and  dextro-malic  acid,  and  between  inactive 
lactic  and  dextro-lactic  acid.  This  case  is,  however,  of  special 
interest,  as  it  was  the  first  one  of  the  kind  studied.  The  relations 
were  discovered  by  means  of  the  experiment  described  below. 

When  a  solution  of  the  ammonium-sodium  salt  of  racemic 
acid,  (NH4)]Sra  ,  C4H406,  is  allowed  to  evaporate  spontaneously, 
beautiful  large  crystals  are  deposited.  On  examining  these 
carefully,  they  are  found  to  be  of  two  kinds.  On  the  crystals 
of  one  kind  certain  hemihedral  faces  are  developed,  while  on 
the  crystals  of  the  other  kind  the  complementary  hemihedral 
faces  are  developed;  so  that  if  a  crystal  of  one  kind  is  placed 
in  front  of  a  mirror,  its  reflection  will  represent  the  arrange- 
ment of  the  hemihedral  faces  occurring  on  a  crystal  of  the 
other  kind.  The  crystals  can  be  separated  into  right-handed,  or 
those  which  have  the  right-handed  hemihedral  faces,  and  left- 
handed,  or  those  which  have  the  left-handed  hemihedral  faces. 


180  DERIVATIVES   OF   THE   PARAFFINS 

On  separating  the  acid  from  the  right-handed  crystals  it  is 
found  to  be  ordinary  dextro-rotatory  tartaric  acid;  while  the  acid 
from  the  left-handed  crystals  is  an  isomeric  substance  called 
levo-rotatory  tartaric  acid.  When  these  two  varieties  of  tartaric 
acid  are  brought  together  in  solution,  they  unite,  the  action  being 
attended  by  an  elevation  of  temperature,  and  the  result  is  ra* 
cemic  acid.  These  phenomena  were  first  observed  by  Pasteur. 

By  crystallizing  cinchonine  racemate  from  alcohol  it  can  be 
resolved  into  the  dextro  and  levo  varieties,  from  which  the 
corresponding  active  acids  can  be  obtained. 

It  will  thus  be  seen  that  racemic  acid  consists  of  two  opti- 
cally active  substances  in  combination,  one  of  which,  ordinary 
tartaric  acid,  is  dextro-rotatory,  and  the  other  levo-rotatory. 

As  has  already  been  stated,  both  inactive  malic  acid  and  in- 
active lactic  acid  have  been  resolved  into  two  active  varieties, 
one  of  which  is  dextro-rotatory,  and  the  other  levo-rotatory. 

3.  Inactive  tartaric  acid,  mesotartaric  acid,  anti- 
tartaric  acid,  C4H6O6  +  H2O,  is  similar  to  racemic  acid.  It 
is  formed  together  with  racemic  acid  by  treating  di-brom- 
succinic  acid  with  silver  oxide  and  water.  It  is  optically  in- 
active. Unlike  racemic  acid  it  cannot  be  resolved  into  the 
optically  active  forms,  and  it  is  believed  that  the  inactivity  is 
due  to  "  internal  compensation." 

The  following  explanation  will  serve  to  make  the  relations 
between  the  four  tartaric  acids  clear:  Tartaric  acid  contains 
two  asymmetrical  carbon  atoms  (see  p.  166),  each  one  of  which 
is  in  combination  with  (1)  a  hydrogen  atom,  (2)  a  hydroxyl, 
(3)  acarboxyl,  and  (4)  the  group,  CH(OH).C02H:  — 

H 
I 
HO  -  C  -  C02H 

I 

HO-C-C02H 
I 
H, 


HYDKOXY-ACIDS  181 

There  are  two  ways  in  which  these  four  groups  can  be  arranged 
around  each  asymmetrical  carbon  according  to  the  hypothesis 
already  explained  under  the  lactic  acids  (which  see).  One 
arrangement  makes  the  substance  dextro-rotatory,  the  other 
makes  it  levo-rotatory.  Now,  if  the  arrangement  around  both  of 
the  carbon  atoms  is  the  same,  the  substance  will  be  optically 
active.  Thus  the  existence  of  the  dextro-acid  and  of  the  levo- 
acid  can  be  explained.  The  racemic  modification,  in  this  case 
racemic  acid,  being  formed  by  combination  of  the  dextro-acid 
with  the  levo-acid  is  inactive.  But,  further,  if  in  one  half  of 
the  molecule  there  is  the  right-handed  arrangement,  and  in  the 
other  half  the  left-handed  arrangement,  the  substance  will  be 
inactive  by  "internal  compensation,"  and  will  not  be  capable 
of  resolution  into  two  optically  active  products.  This  is  be- 
lieved to  be  the  condition  in  mesotartaric  acid.  These  rela- 
tions cannot  be  made  entirely  clear  by  words  and  formulas. 
Models,  which  can  be  easily  constructed  of  stiff  wire  and 
wooden  balls,  are  necessary  to  make  them  clear.  Formulas 
may,  however,  be  used  to  recall  the  arrangements  in  space  that 
are  represented  in  the  models.  The  following  formulas  are 
used  to  show  the  difference  between  the  two  active  acids  and 
mesotartaric  acid:  — 

C02H  C02H  C02H 

!  I  I 

HO-C-H  H-C-OH  HO-C-H 

I  I  I 

H-C-OH  HO-C-H  HO-C-H 

I  1  I 

C02H.  C02H.  C02H. 

Levo-tartaric  acid  Dextro-tartanc  acid  Inactive  mesotartaric  acid 


HYDROXY-ACIDS,  CnH2n_407 

These  are  mono-hydroxy-tribasic  acids.      Citric  acid  is  the 
only  one  known. 


182  DERIVATIVES   OF    THE   PARAFFINS 

/  f  CO2H 

Citric    acid,    CeHsOr  +  H2O  (  CsHXOH)  \  CO-H  .  —  Citric 

\  I 


acid,  like  malic  and  tartaric  acids,  is  widely  distributed  in 
nature  in  many  varieties  of  fruit,  especially  in  lemons,  in 
which  it  occurs  in  the  free  condition.  It  is  found  in  currants, 
whortleberries,  raspberries,  gooseberries,  etc.,  etc. 

It  is  prepared  from  lemon  juice,  and  also  by  the  fermenta- 
tion of  glucose  by  citromyces  pfefferianus  and  a  few  other  fer- 
ments. After  the  fermentation  the  mass  is  treated  with  lime. 
The  calcium  salt  thus  obtained  in  the  form  of  a  precipitate,  is 
collected,  and  decomposed  with  sulphuric  acid.  One  hundred 
parts  of  lemons  yield  5J  parts  of  the  acid. 

Citric  acid  crystallizes  in  rhombic  prisms  which  are  very 
easily  soluble  in  water.  The  crystallized  acid  melts  at  100°, 
the  anhydrous  at  153°  to  154°.  Heated  to  175°  it  loses  water 
and  yields  aconitic  acid  (which  see)  :  —  • 

C3H4(OH)(C02H)3  =  C3H3(C02H)3  +  H20. 

Aconitic  acid 

Aconitic  acid  takes  up  hydrogen,  and  is  transformed  into 
tricarballylic  acid  (which  see).  Thus  a  clear  connection  be- 
tween tricarballylic  acid  and  citric  acid  is  traced;  the  latter 
is  hydroxy-tricarballylic  acid.  Citric  acid  can  be  made  from 
dichloracetone  by  first  converting  this  into  acetone-dicarboxylic 
acid  :  — 

ro  .  CH2C1      ro     CH2CX      CQ     CH2C02H 
<  CH2C1^        <  CH2CN~*         <  CH2C02H' 

The  acetone-dicarboxylic  afcid  is  then  treated  with  hydrocyanic 
acid  and  the  nitril  thus  formed  hydrolyzed  as  shown  below  :  —  • 

CH2.C02H  CH2.C02H 

CO  +  HCN=C<PAr       J 

I  I 

CH2.C02H  CH2.C02H 


HYDROXY-ACIDS  183 

CH2.C02H  CH2.C02H 


CH2.C02H  CH2.C02H 

This  synthesis  shows  that  the  hydroxyl  in  citric  acid  is  in 
combination  with  the  central  carbon  atom. 

When  rapidly  heated  to  a  temperature  above  175°,  citric  acid 
first  gives  aconitic  acid,  then  loses  water  and  carbon  dioxide 
and  gives  itaconic  anhydride  (see  itaconic  acid).  This 
anhydride  is  then  partly  converted  into  citraconic  anhydride 
(see  citraconic  acid)  by  the  action  of  heat. 

Citrates.     A  few  of  the  salts  of  citric  acid  are  :  — 

Mono-potassium  citrate,  KH2  .  C6H507  +  2  H20  ; 

Di-potassium  citrate,  K2H  .  C6H507  ; 

Tri-potassium  citrate,  K3  .  C6H507  -f  H20.  All  these  potas- 
sium salts  are  easily  soluble  in  water. 

Calcium  citrate,  Ca3(C6H507)2  -f  4  H20.  This  salt  is  formed 
by  mixing  a  citrate  of  an  alkali  with  calcium  chloride.  It  is 
more  easily  soluble  in  cold  than  in  hot  water;  hence  boiling 
causes  a  precipitate  in  dilute  solutions. 

Magnesium  citrate,  Mg3(C6H507)2  +  14  H20.  This  is  made  by 
dissolving  magnesia  in  citric  acid.  It  is  used  in  medicine. 

HYDROXY-ACIDS,  CnH2n_2Og 

It  has  been  pointed  out  that  the  hex-acid  alcohols  are 
converted  by  oxidation  into  pentahydroxy-monobasic  acids. 
By  further  oxidation  these  pentahydroxy-monobasic  acids 
are  converted  into  tetrahydroxy-dibasic  acids.  Thus  sorbite, 
CH2OH(CHOH)4CH2OH,  when  oxidized,  yields,  first,  glu- 
conic  acid,  CH2OH(CHOH)4C02H,  and  then  saccharic  acid, 
C02H(CHOH)4C02H,  a  tetrahydroxy-dibasic  acid.  Corre- 
sponding to  each  gluconic  acid  there  is  a  saccharic  acid.  So 
also  the  mannonic  acids  yield  mannosaccharic  acids,  which  are 
dibasic  and  isomeric  with  the  saccharic  acids  ;  and  galactonio 


184  DERIVATIVES    OF   THE   PARAFFINS 

acid   yields    mucic   add.     The    best-known   members   of  this 
group  are  saccharic  and  mucic  acids. 


Saccharic    acid,     C6HioO8    aH4(OH)4  <  •  —  The 

A  OU2xl/ 

dextro   variety   is   formed   by   the   oxidation   of   cane  sugar, 
d-glucose,  sugar  of  milk,  or  starch  with  nitric  acid. 

It  is  an  amorphous  mass  that  becomes  solid  only  with  diffi- 
culty. When  treated  with  hydriodic  acid  it  is  reduced  to 
adipic  acid,  a  member  of  the  oxalic  acid  series  (see  table,  page 
143)  :  — 


<  +  8  HI  =  C4H8  <  +  4  H20  +  8  I. 

Saccharic  acid  Adipic  acid 


Mucic    acid,     C6HioOs   c4H4(OH)4  <  —  This    is 

\  L»(JjM/ 

formed  by  the  oxidation  of  sugar  of  milk,  the  gums,  dulcite, 
or  galactose  with  nitric  acid.  It  is  best  prepared  from  sugar 
of  milk. 

It  is  a  crystalline  powder  that  is  very  difficultly  soluble 
in  cold  water.  Hydriodic  acid  reduces  it  to  adipic  acid  (see 
above,  under  Saccharic  acid). 

When  heated  with  pyridine  to  140°,  mucic  acid  is  changed 
to  the  isomeric  form,  allomucic  add. 


CHAPTER  XI 
CARBOHYDRATES 

AMONG  the  mixed  compounds  are  the  important  substances 
commonly  known  as  carbohydrates.  This  name  was  originally 
given  to  them  because  they  consist  of  carbon  in  combination 
with  hydrogen  and  oxygen,  which  two  elements  are  generally 
contained  in  them  in  the  proportion  to  form  water,  as  shown 
in  the  formulas,  for  glucose,  C6H1206,  starch,  C6H1005,  etc. 
The  name  is,  however,  inaccurate,  as  some  substances  belong- 
ing to  this  group  are  now  known  that  do  not  contain  hydrogen 
and  oxygen  in  the  proportion  to  form  water.  Such  a  sub- 
stance, for  example,  is  rhanmose,  C6H1205.  Further,  there  are 
some  carbon  compounds,  as,  for  example,  formic  aldehyde, 
CH2O,  acetic  acid,  C2H40W  and  lactic  acid,  C3H6O3,  that  con- 
tain hydrogen  and  oxygen  in  the  proportion  characteristic  of 
most  of  the  carbohydrates  but  do  nqt  belong  to  this  group. 
The  name  carbohydrate  has,  however,  been  used  so  long  that 
it  would  be  difficult  to  supplant  it. 

The  carbohydrates  may  be  conveniently  classified  under 
three  heads.  These  are :  — 

1.  Monosaccharides  or  simple  sugars.  —  Examples  cf  these 
are  glucose,  fructose,  arabinose,  and  mannose. 

2.  Poly  sacchar  ides  or  complex  sugars.  —  Examples  are  cane 
sugar,  sugar  of  milk,  maltose,  and  isomaltose. 

3.  Polysaccliarid.es,  that  are  not  sugars.  —  Examples  are  cel- 
lulose, starch,  and  gums. 

The  rnonosaccharides  are  the  simplest  carbohydrates.  Those 
which  are  best  known  have  the  composition  C6H1206,  and  are 
related  to  the  hex-acid  alcohols,  sorbite  and  mannite,  C6H8(OH)6. 
There  are,  however,  simpler  ones,  such  as  arabinose,  C5H100W 

185 


186  CARBOHYDRATES 

erythrose,  C4H804,  and  glycerose,  C3H603;  and  some  that  are 
more  complex,  as  heptose,  C7H1407,  octose,  C8H1608,  and  nonose, 
C9H1809.  The  monosaccharides,  therefore,  fall  into  classes 
which  are  called  trioses,  tetroses,  pentoses,  hexoses,  etc.,  accord- 
ing to  the  number  of  oxygen  atoms  contained  in  them. 

By  methods  that  will  be  explained  below,  it  has  been  shown 
that  the  monosaccharides  or  simple  sugars  are  aldehyde-alcohols 
(aldoses)  or  ketone-alcohols  (ketoses). 

1.   MONOSACCHARIDES 
A.    Trioses  and  Tetroses 

Glycerose,  C3H6O3.  —  This  sugar  deserves  special  mention 
because  it  is  the  simplest  member  of  the  group  of  monosacchar- 
ides, and  because  it  has  been  obtained  artificially.  It  is  formed 
by  treating  glycerol  with  mild  oxidizing  agents,  as,  for  example, 
bromine  and  sodium  hydroxide.  It  is  a  mixture  of  glyceric 
aldehyde  and  dioxyacetone,  the  relations  of  which  to  glycerol 
are  shown  by  the  following  formulas  :  — 


r<"pYATj\  ^2  r<TT/r4TT\  ^ 

H)<CH2OH'  H)<CH2OH'  CH2OH 

Glycerol  Glyceric  aldehyde  Dioxyacetone 

Glycerose  is  a  syrup  that  undergoes  fermentation  and  reduces 
alkaline  solutions  of  copper  salts,  acting  thus  like  many  of  the 
sugars.  Glyceric  aldehyde  is  a  simple  example  of  an  aldose 
or  aldehyde-alcohol,  and  dioxyacetone  is  the  simplest  example 
of  a  ketose  or  ketone-alcohol. 

When  the  mixture  of  these  two  substances  is  treated  with 
caustic  soda  it  is  converted  into  i-acrose,  a  sugar  of  special 
importance,  as  it  forms  the  starting  point  in  the  synthetical 
operations  that  lead  to  the  formation  of  all  the  members  of 
the  glucose  group. 

Erythrose,  C4H8O4,  has  been  obtained  from  erythrite  in 
the  same  way  that  glycerose  is  obtained  from  glycerol. 


MONOSACCHARIDES  187 

B.  Pentoses 

Arabinoses,  C5H10O5.  —  Ordinary  arabinose  is  obtained  from 
gum  arabic  and  cherry  gum  by  boiling  with  dilute  sulphuric 
acid.  This  variety  is  called  levo-arabinose  on  account  of  its  re- 
lation to  levo-glucose  and  levo-mannose,  although  it  turns  the 
plane  of  polarization  to  the  right.  Dextro-arabinose  and  in- 
active arabinose  have  also  been  obtained,  the  latter  by  com- 
bination of  the  levo  and  dextro  varieties. 

Xylose,  C5H10O5,  is  obtained  from  wood  gum  by  boiling 
with  dilute  acids. 

Ribose,  C5H10O5,  stereoisomeric  with  arabinose,  is  formed 
by  oxidation  of  adonite  and  yields  adonite  by  reduction. 

Rhamnose,  C6H12O5,  has  been  obtained  by  the  breaking 
down  of  a  number  of  natural  substances,  such  as  quercitrin. 
It  has  been  shown  to  be  a  methyl  derivative  of  a  pentose,  and 
is  therefore  to  be -represented  by  the  formula  CH3.C5H9O5. 

C.  Hexoses 

Glucose,  grape  sugar  (dextrose),  CeHiaOe+EkO.— Glucose 
occurs  very  widely  distributed  in  the  vegetable  kingdom, 
especially  in  sweet  fruits,  in  which  it  is  found  together  with 
an  equivalent  quantity  of  fructose  or  fruit  sugar.  It  is  also 
found  in  honey,  together  with  fructose ;  and,  further,  in  the 
blood,  in  the  liver,  and  in  the  urine.  In  the  disease  Diabetes 
mellitus  the  quantity  contained  in  the  urine  is  largely  in- 
creased, reaching  as  high  as  180  to  360  grams  per  day. 

Glucose  is  formed  from  several  of  the  carbohydrates  of  the 
formulas  C^H^On  and  C6H1005,  by  boiling  them  with  dilute 
mineral  acids,  or  by  the  action  of  enzymes.  The  formation 
from  cane  sugar  takes  place  according  to  this  equation,  equiva- 
lent quantities  of  glucose  and  fructose  being  formed :  — 

CuHaOu  +  H20  =  C6H1206  +  C6H1206- 

Cane  sugar  Glucose  Fructose 


188  CARBOHYDRATES 

Starch,  cellulose,  and  dextrin  yield  glucose   according  to 
this  equation  :  — 

C6H1005 


Finally,  glucose  occurs  in  nature,  in  combination  with  a 
number  of  carbon  compounds,  in  the  so-called  glucosides. 
These  break  up  easily  when  treated  with  dilute  mineral  acids 
or  ferments,  and  yield  glucose  as  one  of  the  products  (see 
Glucosides).  Examples  of  the  glucosides  are  amygdalin, 
aesculin,  salicin,  etc. 

Glucose  is  prepared  on  the  large  scale  from  corn  starch  in 
the  United  States,  and  from  potato  starch  in  Germany.  The 
transformation  is  usually  effected  by  boiling  with  dilute  sul- 
phuric acid.  The  acid  is  then  removed  by  treating  the 
solutions  with  chalk,  and  filtering.  The  filtered  solutions  are 
evaporated  down  either  to  a  syrupy  consistency,  an-d  sent  into 
the  market  under  the  names  "  glucose,"  "  mixing  syrup,"  etc., 
or  to  dryness,  the  solid  product  being  known  in  commerce  as 
"grape  sugar."  By  evaporating  the  solutions  down  to  such 
a  concentration  that  they  contain  from  12  to  15  per  cent  of 
glucose,  crystals  are  formed  that  closely  resemble  those  of 
cane  sugar.  They  consist  of  anhydrous  grape  sugar.  Their 
formation  is  facilitated  by  adding  a  little  of  the  crystallized 
substance  to  the  concentrated  solutions.  Glucose  crystallizes 
from  concentrated  solutions,  usually  in  crystalline  masses  con- 
sisting of  minute  six-sided  plates  which  contain  one  molecule 
of  water.  The  mass,  as  seen  in  commercial  "granulated  grape 
sugar,"  looks  like  granulated  sugar.  It  crystallizes  from 
alcohol  in  monoclinic  crystals.  The  sweetness  of  glucose  is 
to  that  of  cane  sugar  as  3  to  5.  Its  solutions  turn  the  plane  oj 
polarization  to  the  right. 

If  in  the  treatment  of  starch  with  sulphuric  acid  the  trans- 
formation is  not  complete,  and  this  is  usually  the  case,  the  prod- 
uct is  a  mixture  of  glucose,  maltose,  and  dextrin.  The  longer 
the  action  continues,  the  larger  the  percentage  of  glucose. 


GLUCOSE  189 

Gluoose  is  easily  oxidized,  reducing  the  salts  of  silver  and 
copper.  When  treated  with  nascent  hydrogen,  it  yields  sorbite 
(which  see).  Under  the  influence  of  yeast  it  ferments,  yielding 
mainly  alcohol  and  carbon  dioxide.  Putrid  cheese  transforms 
it  first  into  lactic  acid  and  then  into  butyric  acid  by  the  so- 
called  lactic  acid  fermentation. 

Glucose  forms  compounds  with  metals  and  salts.  Among 
the  better  known  compounds  of  this  kind  are  those  mentioned 
below :  — 

Sodium  glucose C6HU08 .  Na ; 

Sodium  chloride  glucose     .     .     2  C6H1206 .  NaCl  •+•  H20 ; 
also         CeHjA .  NaCl  -f  JH,  0,  and  C^Oe .  2  NaCL 

These  compounds,  with  sodium  chloride,  crystallize  well,  and 
can  be  easily  obtained  in  pure  condition. 

Cupric  oxide  glucose  ....     CeH^Og .  5  CuO. 

By  treatment  with  acetic  anhydride,  glucose  yields  a  product 
containing  five  acetyl  groups,  pent-acetyl-glucose, 

C6H7(C2H30)506- 

NOTE  FOR  STUDENT.  —  What  does  the  formation  of  this  compound 
indicate? 

It  is  often  important  to  know  the  quantity  of  glucose  con- 
tained in  a  given  liquid ;  as,  for  example,  in  the  urine  in  a  case 
of  suspected  diabetes.  For  the  purpose  of  making  the  estima- 
tion, advantage  is  taken  of  the  action  of  glucose  towards  an 
alkaline  solution  of  copper  sulphate.  The  solution  commonly 
used  is  that  known  as  Fehling's  solution.  It  is  prepared  by 
dissolving  34.64*  crystallized  pure  copper  sulphate  in  200CC 
water,  adding  a  solution  of  150g  potassium  tartrate,  and  90g 
sodium  hydroxide,  and  diluting  so  that  the  whole  makes  one 
litre. 

Experiment  38.  Make  half  the  quantity  of  Fehling's  solution  above 
mentioned,  and  put  in  a  bottle  with  a  glass  stopper.  In  a  test-tube  boil 
about  10°°  of  this  solution,  and  then  add  a  few  drops  of  a  dilute  solution 


190  CARBOHYDRATES 

of  glucose.  Continue  to  boil,  and  add  a  little  more  of  the  glucose  solution; 
and  so  on,  until,  on  removing  the  tube  from  the  lamp,  a  dark-red  uniform- 
looking  precipitate  settles,  leaving  the  liquid  above  it  perfectly  clear  and 
colorless.  This  precipitate  is  cuprous  oxide.  By  taking  proper  precau- 
tions, the  exact  amount  of  glucose  present  in  a  solution  can  be  estimated 
in  this  way. 

Ordinary  glucose  is  known  as  d-glucose  on  account  of  its 
dextro-rotatory  power.  Both  /-glucose  and  i-glucose  have  been 
made. 

Fructose,  fruit  sugar  (levulose),  C6H1206.  —  This  sugar 
occurs  together  with  glucose,  and  in  equivalent  quantities,  in 
fruits ;  and  is  formed  by  the  action  of  dilute  mineral  acids,  or 
invertase,  on  cane  sugar.  Pure  fructose  is  obtained  by  heating 
inulin,  a  carbohydrate  of  the  formula  C^H^Ou,  with  very  dilute 
acids.  It  is  also  formed  with  mannose  by  careful  oxidation  of 
d-mannite. 

Ordinary  fructose  is  called  d-fructose,  although  it  turns  the 
plane  of  polarization  to  the  left.  The  reason  for  this  is  that  it 
is  related  to  other  substances  that  are  dextro-rotatory. 

Fructose  can  be  obtained  in  the  form  of  crystals.  It  is  about 
as  sweet  as  cane  sugar,  and  has  been  proposed  as  a  substitute 
for  this  in  diabetes. 

i-Fructose  has  been  made  artificially  in  three  ways :  — 

1.  By  polymerization  of  formic  aldehyde,  CH20,  by  means 
of  bases ; 

2.  By  successive  treatment  of   acrolem  with  bromine  and 
baryta  water ; 

3.  By  the  action  of   dilute  alkali  on  glycerose,  which  is 
formed  by  oxidation  of  glycerol. 

It  will  be  observed  that  formic  aldehyde  has  the  same  per- 
centage composition  as  fructose. 

When  acrolem  is  treated  with  bromine,  two  atoms  of  the 
latter  are  added  directly  to  the  former :  — 

CH2:  CH .  COH  -f  2  Br  =  CH2Br .  CHBr .  COH. 


FRUCTOSE  191 

When  this  dibromide  is  treated  with  baryta  water,  hydroxyl 
is  first  substituted  for  bromine,  and  glyceric  aldehyde  and 
dihydroxyacetone  are  the  first  products.  These  are  then  con- 
densed and  form  ^-fructose :  — 

CH2Br  .  CHBr  .  COH  +  Ba(OH)2 

=  CH2OH .  CHOH  .  COH  +  BaBr2. 

Glyceric  aldehyde  is,  however,  not  the  only  product  of  this 
reaction.  Dihydroxyacetone,  JDHgOH  —  CO  —  jgH2OH,  is  also 
formed,  as  is  shown  by  the  reactions  of  the  product.  The 
formation  of  i-fructose  from  glycerose  takes  place  as  repre- 
sented in  the  following  equation :  — 

CH2OH  -  CHOH  -  CHO  +  CH2OH  -  CO  -  CH2OH 

=  CH2OH  -  CHOH  -  CHOH  -  CHOH  -  CO  -  CH2OH. 

The  oxygen  atom  of  the  aldehyde  group,  CHO,  unites  with  a 
hydrogen  atom  of  one  of  the  CH2  groups  of  the  dihydroxy- 
acetone, forming  hydroxyl,  and  this  makes  possible  the  union 
of  the  residue  of  the  glyceric  aldehyde  with  that  of  the 
dihydroxyacetone. 

This  reaction  is  known  as  the  aldol  condensation,  because  the 
product  first  obtained  in  this  way  was  called  aldol.  This  is 
formed  by  condensation  of  ordinary  aldehyde  thus  :  — 

CH3 .  CHO  +  CH3 .  CHO  =  CH3 .  CHOH .  CH2 .  CHO. 

Aldol 

Aldol  is  really  /3-hydroxbutyric  aldehyde. 

On  account  of  the  formation  of  i-fructose  from  acrolein,  it 
was  called  acrose.  It  was  later  shown  to  be  the  inactive 
variety  of  fructose,  and  the  name  acrose  became  unnecessary, 
though  it  is  still  used. 

When  ^-fructose  is  treated  with  yeast,  it  is  partly  trans- 
formed by  the  ferment  into  alcohol  and  carbon  dioxide.  It  is 
the  d-fructose  contained  in  it  that  undergoes  the  change,  while 
the  Z-fructose  remains  unchanged,  and  can  be  obtained  free 
from  the  other  two  varieties. 


192  CAEBOHYDRATES 

Constitution  of  glucose  and  fructose.  —  Two  reactions  have 
been  of  special  value  in  the  determination  of  the  constitution 
of  the  members  of  the  group  of  monosaccharides. 

a.  When  either  an  aldehyde  or  an  acetone  is  treated  with 
hydrocyanic  acid  an  addition-product  is  formed  thus  :  — 

H  H 


The  products  can  be  converted  into  corresponding  acids  by 
the  change  of  the  cyanogen  group  into  carboxyl.  Thus  the 
nitril  from  aldehyde  yields  a-hydroxypropionic  (or  lactic) 
acid  :  — 

H  H 

CH3.  C  <  °  J  +  2  H20  =  CH3.  C  <  J^OH  +  NH3; 


while  the  nitril  from  acetone  yieldsa-hydroxyisobutyricacid:  — 

CH3  OH  CH3  OH 

CH3>     <CN+2H2°=CH3>     <COOH4     H* 

By  the  aid  of  these  reactions  it  has  been  shown  that  glucose 
is  an  aldose,  and  fructose  a  ketos 

(1)  CHO  -  CHOH  -  CHOH  -  CHOH  -  CHOH  -  CH2OH. 

Glucose 

(2)  CH2OH  -  CO  -  CHOH  -  CHOH  -  CHOH  -  CH2OH. 

Fructose 

By  adding  hydrocyanic  acid  to  a  compound  of  formula  (1)  a 
nitril  of  the  following  formula  is  formed  :  — 

~" 

>  CH  -  CHOH  -  CHOH  -  CHOH  -  CHOH  -  CH2OH. 


GLUCOSE   AND   FRUCTOSE  193 

This  yields  an  acid  of  the  formula 

>  CH  ~  CHOH  -  CHOH  -  CHOH  -  CHOH-CH2OH. 


By  treating  this  with  hydriodic  acid  it  is  reduced  to  the 
acid 

H02C.CH2.CH2.CH2.CH2.CH2.CH3. 

The  acid  obtained  from  glucose  by  means  of  the  above  re- 
actions has  the  structure  represented  by  this  formula,  and  it 
hence  follows  that  glucose  itself  must  have  the  structure 
represented  by  formula  (1)  above,  or  it  must  be  an  aldose. 

By  subjecting  fructose  to  the  same  processes,  the  product 
obtained  has  the  structure 

C02H 
I 
CH3  .  CH  .  C  it  2  •  CH2  .  CH2  .  CH3  j 

and  it  follows  from  this  that  fructose  must  have  the  structure 
represented  by  formula  (2)  above,  or  it  must  be  a  ketose. 

b.  When  an  aldehyde  or  a  ketone  is  treated  with  phenyl- 
hvjdrazine,  CgH^  .  NH  .  NH2,  ,a  reaction  takes  place,  as  repre- 
sented in  this  equation:  — 

H  H 

I  I 

ECO  +  H2N  .  NHC6H5  =  E  .  CN  .  NHC6H5  +  H20. 

The  products  thus  formed  are  called  phenylhydrazones. 
The   sugars   form   hydrazones   when  treated    with   phenyl 
hydrazine.     Thus  glucose  and  fructose  give  the  products 

(1)  CH2OH.  CHOH.  CHOH.  CHOH.  CHOH.  CH 


Phenylhydrazone  of  Glucose 

(2)   CH2OH.  CHOH.  CHOH.  CHOH.  C.CH2OH 

II 
N.NHC6H6. 

Phenylhydrazone  of  Fructose 


194  CARBOHYDRATES 

If  the  sugars  are  boiled  with  an  excess  of  phenylhydrazine  a 
second  reaction  takes  place.  In  the  case  of  glucose,  the  CHOH 
group  adjoining  the  carbon  atom  with  which  the  residue  of 
phenylhydrazine  is  combined,  loses  two  hydrogen  atoms  and  is 
converted  into  the  ketone  group  CO.  Then  phenylhydrazine 
reacts  with  this,  and  forms  a  product  of  the  formula 

CH2OH  •  CHOH  •  CHOH  •  CHOH .  C  •  CH 

II    II 
C6H5HN.N  N.NHC6H5. 

This  is  called  phenylglucosazone. 

In  the  case  of  fructose,  the  primary  alcohol  group,  CH2OH, 
adjoining  the  carbon  atom  with  which  the  residue  of  phenyl- 
hydrazine is  combined  is  changed  to  the  aldehyde  group,  CHO, 
and  then  phenylhydrazine  reacts  with  this  in  the  usual  way, 
giving  a  product  of  the  formula 

CH2OH. CHOH. CHOH. CHOH. C.CH 

II    II 
C6H5HN.NN.NHC6H5. 

This  is  the  phenylfructosazone.  Phenylglucosazone  and 
phenylfructosazone  are  identical. 

The  osazones  are  in  general  difficultly  soluble  in  water  and 
have  characteristic  properties  whereby  they  can  be  recognized. 
The  sugars  themselves  are  easily  soluble  and  it  is  hard  to 
separate  them,  and  until  the  discovery  of  the  phenylhydrazine 
reaction  the  investigation  of  the  sugars  advanced  very  slowly. 
This  reaction  in  the  hands  of  one  of  the  most  skilful  experi- 
menters, Emil  Fischer,  has  greatly  advanced  our  knowledge  of 
the  sugar  group  within  a  few  years  past. 

The  formation  of  the  osazones  makes  it  possible  to  recognize 
the  different  sugars,  but  it  does  not  give  the  sugars  themselves. 
The  regeneration  of  the  sugars  from  the  osazones  is  of  great 
importance.  The  principal  reactions  available  for  the  purpose 
are  the  following  :  — 

1.   The  osazone  is   heated  for  a  short  time  with  fuming 


GALACTOSE  195 

hydrochloric  acid,  when  it  yields  phenylhydrazine  hydrochlo- 
ride  and  an  osone,  thus  :  — 

CH2OH  .  (CHOH)3  .  C  .  CH  +  2  H20  +  2  HC1 

II     II 


=  CH2OH(CHOH)3CO  .  CHO  +  2  C6H5  .  NH  .  NH2  .  HC1. 

Osone 

2.  The  osone  can  be  isolated  and  reduced  by  means  of  acetic 
acid  and  zinc  dust,  when  it  is  converted  into  the  corresponding 
ketose  :  — 

CH2OH(CHOH)3CO  .  CHO  +  2  H 

=  CH2OH(CHOH)3  .  CO  .  CH2OH. 

Whether  the  original  sugar  was  an  aldose  or  a  ketose,  tha 
final  product  of  the  above  series  of  reactions  is  a  ketose.  The 
aldoses  cannot,  therefore,  be  regenerated  in  this  way.  On 
the  other  hand,  any  aldose  can  be  converted  into  a  ketose  by 
this  means. 

Mannose,  C6Hi2O6.  —  d-Mannose  is  one  of  the  products  of 
oxidation  of  d-mannite,  and  is  obtained  by  the  action  of  dilute 
acids  on  some  kinds  of  cellulose.  The  shavings  formed  in  the 
manufacture  of  buttons  from  vegetable  ivory  are  rich  in  the 
cellulose  which  yields  d-mannose. 

^-Mannose  and  i-mannose  have  also  been  prepared. 
The   mannoses    are    aldoses,   and    are    stereoisomeric   with 
glucose. 


Galactose,  CeHioOe-  —  d-Galactose  is  formed  by  treatment 
of  sugar  of  milk  with  dilute  acids,  d-glucose  being  formed  at 
the  same  time.  Other  carbohydrates  also  yield  it.  I-  and 
i-Galactoses  are  known.  By  reduction  d-  and  Z-galactoses  are 
transformed  into  dulcite.  By  oxidation  all  three  galactoses 
yield  mucic  acid. 


196  CARBOHYDRATES 


Gulose,  CeHiiOe-  —  The  three  guloses  have  been  made  arti- 
ficially. They  are  aldoses  corresponding  to  the  three  sorbites, 
and  are  stereoisomeric  with  the  glucoses. 

The  method  by  which  Z-gulose  was  made  is  of  special  inter- 
est, as  it  is  based  upon  reactions  that  may  be  used  for  passing 
from  any  aldose  to  one  containing  one  carbon  atom  more.  It 
consists  in  adding  hydrocyanic  acid  to  the  aldose,  converting 
the  nitril  thus  obtained  into  the  corresponding  acid,  and  then  re- 
ducing the  acid.  Thus  in  the  case  of  £-gulose  the  starting-point 
is  xylose,  and  the  steps  may  be  briefly  represented  thus  :  — 


Xylose  ->  (HCN)   2   hydrocyanides  ->  ^ulonic 

J-idonic  acid 


7      , 

(reduction)  ^ulose 
Z-idose. 


Talose  and  idose  are  isomeric  with  glucose.  They  have  only 
been  made  artificially. 

2.     POLYSACCHARIDES    OR    COMPLEX    SUGARS 

The  polysaccharides,  or  complex  sugars,  are  found  in  nature, 
as,  for  example,  cane  sugar  and  sugar  of  milk,  or  are  formed 
from  more  complex  carbohydrates,  as,  for  example,  maltose 
from  starch.  Their  most  characteristic  property  is  their  power 
to  break  down  into  monosaccharides  under  the  influence  of 
dilute  acids  or  enzymes.  The  reaction  involves  the  addition 
of  the  elements  of  water,  and  is  called  hydrolysis.  A  simple 
example  of  this  kind  of  action  is  the  conversion  of  maltose 
into  d-glucose:  — 

C12H22Ou  +  H20=2C6H12Oa. 

Maltose  d-Glucose 

In  most  cases  the  hydrolysis  of  a  polysaccharide  gives  more 
than  one  monosaccharide.  Cane  sugar,  for  example,  gives 
eZ-glucose  and  d-fructose  :  — 

Ci2H220,i  +  H20  =  C6H1206  +  C6H1206  ; 

Cane  sugar  c/-Glucose          ^-Fructose 


CANE  SUGAR  197 

sugar  of  milk  gives  d-galactose  and  cf-glucose :  — 
CuHaOu  +  H20  =  C6HMOe  +  C6H1206. 

<?-Galactose     (Z-Glucose 

Polysaccharides  that  give  two  monosaccharides  when  hydro, 
lyzed  are  known  as  saccharobioses ;  those  that  give  three,  as 
sa  ccharotrioses. 

Cane  sugar,  saccharose,  Ci2H22On.  —  This  well-known 
variety  of  sugar  occurs  very  widely  distributed  in  nature,  in 
sugar  cane,  sorghum,  the  Java  palm,  the  sugar  maple,  beets, 
madder  root,  coffee,  walnuts,  hazel  nuts,  sweet  and  bitter 
almonds;  in  the  blossoms  of  many  plants;  in  honey,  etc.,  etc. 

It  is  obtained  mainly  from  the  sugar  cane  and  from  beets. 
In  either  case  the  processes  of  extraction  and  refining  are 
largely  mechanical.  When  sugar  cane  is  used,  this  is  macer- 
ated with  water  to  dissolve  the  sugar.  Thus  a  dark-colored 
solution  is  obtained.  This  is  evaporated,  and  then  passed 
through  filters  of  bone-black  which  remove  the  coloring  mat- 
ter. The  solution  is  evaporated  in  the  air  to  some  extent,  and 
then  in  large  vessels  called  vacuum  pans,  from  which  the  air 
is  partly  exhausted,  so  that  the  boiling  takes  place  at  a  lower 
temperature  than  would  be  required  under  the  ordinary 
pressure  of  the  atmosphere.  The  mixture  of  crystals  and 
mother  liquors  obtained  from  the  vacuum  pans  is  freed  from 
the  liquid  by  being  brought  into  the  centrifugals.  These 
are  funnel-shaped  sieves  which,  are  revolved  very  rapidly  ? 
the  liquid  being  thus  thrown  by  centrifugal  force  through  the 
openings  of  the  sieve,  while  t^e  crystals  remain  behind  and 
are  nearly  dried.  The  final  drying  is  effected  by  placing  the 
crystals  in  a  warm  room. 

When  beets  are  used,  the  process  is  essentially  the  same, 
though  there  are  some  differences  in  the  details. 

The  mother  liquors  which  are  obtained  from  the  centrifu- 
gals are  further  evaporated,  and  yield  lower  grades  of  sugar1, 


198  CARBOHYDRATES 

and,  finally,  a  syrup  is  obtained  which  does  not  crystallize. 
This  is  molasses.  Molasses  is  sometimes  brought  into  the 
market  as  such ;  sometimes,  particularly  when  obtained  from 
beet  sugar,  it  is  allowed  to  ferment  for  the  purpose  of  making 
alcohol.  The  spent  wash,  or  waste  liquor,  "  vinasse,"  is  now 
evaporated  to  dry  ness  and  calcined  for  the  purpose  of  getting 
the  alkaline  salts  contained  in  the  residues.  The  products  of 
distillation  are  collected,  and  from  them  tri-methyl-amine  is 
separated  (see  p.  98). 

Sugar  crystallizes  from  water  in  well-formed,  large  mono- 
clinic  prisms.  It  is  dextro-rotatory.  When  heated  to  210°  to 
220°,  cane  sugar  loses  water,  and  is  converted  into  the  sub- 
stance called  caramel,  which  is  more  or  less  brown  in  color, 
according  to  the  duration  of  the  heating  and  the  temperature 
reached.  Boiled  with  dilute  mineral  acids,  cane  sugar  is  split 
into  equal  parts  of  glucose  and  fructose,  as  has  been  stated. 
The  mixture  of  the  two  is  called  invert-sugar.  The  process  is 
called  inversion.  It  takes  place,  to  some  extent,  when  impure 
sugar  is  allowed  to  stand.  Hence  invert-sugar  is  contained  in 
the  brown  sugars  found  in  the  market.  The  enzyme,  invertase 
(see  p.  40),  formed  by  yeast,  gradually  transforms  cane  sugar 
into  glucose  and  fructose,  and  these  then  undergo  fermentation. 
Cane  sugar  itself  does  not  ferment. 

Cane  sugar  does  not  reduce  an  alkaline  solution  of  coppei 
sulphate.  If  the  two  are  boiled  together  for  some  time,  the 
sugar  is  to  some  extent  inverted,  and  to  this  extent  reduction 
of  the  copper  salt  takes  place. 

Experiment  39.  Prepare  a  dilute  solution  of  cane  sugar  by  dissolv- 
ing is  to  2s  in  200CC  water.  Test  t'lis  with  Fehling's  solution,  as  in  Exp. 
38.  Now  add  to  the  sugar  solution  10  drops  concentrated  hydrochloric 
acid,  and  heat  for  half  an  hour  on  the  water-bath  at  100° ;  exactly  neu- 
tralize the  acid  with  a  dilute  solution  of  sodium  carbonate,  and  test  with 
Fehling's  solution. 

Oxidizing  agents  readily  convert  cane  sugar  into  oxalic  acid 
(see  Exp.  34)  and  saccharic  acid. 


SUGAR   OF   MILK  199 

Like  glucose,  cane  sugar  forms  compounds  with  metals, 
metallic  oxides,  and  salts.  Among  these  the  following  may 
be  mentioned :  — 

Sodium  sucrate C12H210U .  Ka, 

Sodium-chloride  sucrate     .     .     C12H220U .  NaCl, 

Calcium  sucrate C^H^On .  Ca, 

and          Lime  sucrate C^^n .  2  CaO. 

These  derivatives  are  not  sweet. 

An  oct-acetate  of  the  formula  C12H14(C2H30)8On  has  been  made 
by  treating  sugar  with  sodium  acetate  and  acetic  anhydride. 

Cane  sugar  is  in  some  way  made  up  by  a  combination  of  a 
molecule  of  c£-glucose  and  a  molecule  of  d-fructose,  with  elimi- 
nation of  a  molecule  of  water.  The  resulting  compound  does 
not  react  with  phenylhydrazine  nor  with  Fehling's  solution, 
and,  therefore,  it  probably  does  not  contain  a  carbonyl  group 
CO.  The  artificial  preparation  of  cane  sugar  from  d-glucose 
and  d-fructose  has  not  been  effected. 

Sugar  of  milk,  lactose,  Ci2H22On  +  H2O. — This  sugar  oc- 
curs in  the  milk  of  all  mammals,  and  is  obtained  in  the  manu- 
facture of  cheese.  The  casein  is  separated  from  the  milk  by 
means  of  rennet;  the  sugar  of  milk  remains  in  solution,  is 
separated  by  evaporation,  and  purified  by  recrystallization.  It 
crystallizes  in  rhombic  crystals.  That  which  comes  into  the 
market  has  been  crystallized  on  strings  or  wood  splinters.  It  has 
a  slightly  sweet  taste ;  is  much  less  soluble  in  water  than  cane 
sugar,  and  is  dextro-rotatory.  It  reduces  Fehling's  solution. 
Oxidized  with  nitric  acid,  it  yields  mucic  and  saccharic  acids. 
Nascent  hydrogen  converts  sugar  of  milk  into  mannite,  dulcite, 
and  other  substances.  Like  glucose  and  cane  sugar,  it  forms 
compounds  with  bases,  dissolving  lime,  baryta,  lead  oxide,  etc. 

Sugar  of  milk  ferments  under  certain  circumstances,  and  is 
thus  converted  into  lactic  acid.  The  souring  of  milk  is  a  result 
of  this  fermentation.  The  lactic  acid  formed  coagulates  the 
casein  j  hence  the  thickening. 


200  CARBOHYDRATES 


Maltose,  C^H^On  .  H2O.  —  This  carbohydrate  is  formed  b^ 
the  action  of  malt  on  starch.  Malt,  which  is  made  by  steeping 
barley  in  water  until  it  germinates,  and  then  drying  it,  con- 
tains a  substance  called  diastase,  which  has  the  power  of  effect- 
ing changes  similar  to  some  of  those  effected  by  the  ferments. 
Thus,  it  acts  upon  starch,  and  converts  it  into  dextrin  and 
maltose  :  — 

3  C6H1005  -f-  H20  =  C^H^On  -f-  C6H1005. 

Starch  Maltose  Dextrin 

Maltose  is  also  formed  by  the  action  of  dilute  sulphuric  acid 
upon  starch,  and  is  hence  contained  in  commercial  glucoses. 
By  further  treatment  with  sulphuric  acid  it  is  converted  into 
glucose.  Maltose  crystallizes  in  fine  needles;  is  dextro-rota- 
tory; reduces  Fehling's  solution;  and  ferments  with  yeast, 
being  first  converted  into  monosaccharides  by  maltase,  which 
is  an  enzyme  contained  in,  or  formed  by,  yeast. 

3.   POLYSACCHARIDES  THAT  ABE  NOT  SUGARS 

Cellulose,  (C^H.WO5)X>  —  Cellulose  is  the  chief  constituent  of 
the  cell  membranes  of  all  vegetable  tissues.  It  presents  dif- 
ferent appearances  and  different  properties,  according  to  the 
source  from  which  it  is  obtained;  but  these  differences  are 
due  to  substances  with  which  the  cellulose  is  mixed;  and 
when  they  are  removed,  the  cellulose  left  behind  is  the  same 
thing,  no  matter  what  its  source  may  have  been.  The  coarse 
wood  of  trees,  as  well  as  the  tender  shoots  of  the  most  delicate 
plants,  all  contain  cellulose  as  an  essential  constituent.  Cot- 
ton-wool, hemp,  and  flax  consist  almost  wholly  of  cellulose. 
It  also  occurs  in  the  animal  kingdom.  Thus  the  tunica  of 
the  Ascidia  is  chiefly  composed  of  cellulose. 

For  the  preparation  of  cellulose,  either  Swedish  filter-paper 
or  cotton-  wool  may  be  taken. 

Experiment  4O.  Treat  some  cotton-wool  successively  with  ether, 
alcohol,  water,  a  caustic  alkali,  and,  finally,  a  dilute  acid.  Then  wash 
with  water. 


GUN   COTTON  201 

Cellulose  is  amorphous ;  insoluble  in  all  ordinary  solvents ; 
soluble  in  an  ammoniacal  solution  of  cupric  oxide.  It  dis- 
solves in  concentrated  sulphuric  acid.  If  the  solution  is 
diluted  and  boiled,  the  cellulose  is  converted  into  .dextrin  and 
glucose.  It  will  thus  be  seen  that  rags,  paper,  and  wood, 
which  consist  largely  of  cellulose,  might  be  used  for  the 
preparation  of  glucose,  and  consequently  of  alcohol. 

Experiment  41.  Dissolve  a  sheet  or  two  of  filter-paper  in  as  small  a 
quantity  of  concentrated  sulphuric  acid  as  will  suffice  ;  dilute  with  water 
to  about  half  to  three-quarters  of  a  litre,  and  boil  for  an  hour.  Remove 
the  sulphuric  acid  by  means  of  chalk ;  filter ;  evaporate ;  and  test  for 
glucose  by  means  of  Fehling's  solution. 

Gun  cotton,  pyroxylin,  nitre-cellulose.  —  Cellulose  has 
some  of  the  properties  of  alcohols ;  among  them  the  power  to 
form  ethereal  salts  with  acids.  Thus,  when  treated  with 
nitric  acid,  it  forms  several  nitrates,  just  as  glycerol  forms  the 
nitrates  known  as  nitro-glycerin  (which  see). 

When  cotton  is  exposed  for  some  time  to  the  action  of  a 
warm  mixture  of  nitre  and  sulphuric  acid,  soluble  gun  cotton  or 
soluble  pyroxylin  is  formed.  This  consists  of  the  lower  nitrates 
(the  di-,  tri-,  and  tetra-nitrates),  which  are  soluble  in  ether 
containing  a  little  alcohol,  and  in  acetone. 

The  solution  is  called  collodion  solution.  When  poured  upon 
the  surface  of  a  solid,  such  as  glass,  the  ether  and  alcohol 
rapidly  evaporate  and  leave  a  thin  coating  of  the  nitrates.  It 
finds  extensive  application  in  surgery  and  in  photography. 

When  treated  with  a  mixture  of  nitric  and  sulphuric  acids, 
cotton  yields  the  higher  nitrates  (tetra-,  penta-,  and  hexa- 
nitrates),  which  are  not  soluble  in  alcohol  and  ether.  These 
are  called  gun  cotton  or  pyroxylin.  They  are  extensively  used 
as  explosives.  Gun  cotton  forms  the  active  constituent  of 
some  of  the  smokeless  powders  now  so  extensively  used.  In 
the  manufacture  of  these  powders  the  gun  cotton  is  gelatinized 
by  treating  it,  in  finely  divided  condition,  with  acetone  or  some 


202  CARBOHYDRATES 

other  similar  solvent.  Under  these  circumstances  the  gun 
cotton  does  not  dissolve,  but  it  swells  up  and  forms  a  gelati- 
nous mass.  From  this  the  solvent  is  removed  by  pressure  and 
evaporation,  and  the  residual  mass  cut  into  laminae,  or  powdered 
by  appropriate  methods.  The  name  "  explosive  gelatin "  is 
given  to  the  substance  prepared  as  above. 

A  solution  of  soluble  cotton  in  molten  camphor  gives  celluloid. 
As  it  is  plastic  at  a  slightly  elevated  temperature,  it  can  easily 
be  moulded  into  any  desired  shape.  When  it  cools  it  hardens. 

Paper.  — Paper  in  its  many  forms  consists  mainly  of  cellu- 
lose. The  essential  features  in  the  manufacture  of  paper  are, 
first,  the  disintegration  of  the  substances  used.  This  is  effected 
partly  mechanically,  and  partly  by  boiling  with  caustic  soda. 
The  mass  is  converted  into  pulp  by  means  of  knives  placed  on 
rollers.  The  pulp,  with  the  necessary  quantity  of  water,  is 
then  passed  between  rollers.  Kags  of  cotton  or  linen  are 
chiefly  used  in  the  manufacture  of  paper;  wood  and  straw 
are  also  used. 

Starch,  (C6HWO5)X.  —  Starch  is  found  everywhere  in  the 
vegetable  kingdom  in  large  quantity,  particularly  in  all  kinds 
of  grain,  as  maize,  wheat,  etc. ;  in  tubers,  as  the  potato,  arrow- 
root, etc. ;  in  fruits,  as  chestnuts,  acorns,  etc. 

In  the  United  States  starch  is  manufactured  mainly  from 
maize ;  in  Europe,  from  potatoes. 

The  processes  involved  in  the  manufacture  of  starch  are 
mostly  mechanical.  The  maize  is  first  treated  with  warm 
water;  the  softened  grain  is  then  ground  between  stones,  a 
stream  of  water  running  continuously  into  the  mill.  The  thin 
milky  fluid  which  is  carried  away  is  brought  upon  sieves  of 
silk  bolting-cloth,  which  are  kept  in  constant  motion.  The 
starch  passes  through  with  the  water  as  a  milky  fluid,  and 
this  is  allowed  to  settle  when  the  water  is  drawn  off.  The 
starch  is  next  treated  with  water  containing  a  little  alkali 
(caustic  soda,  or  sodium  carbonate),  the  object  of  which  is 


STARCH  203 

to  dissolve  gluten,  oil,  etc.  The  mixture  is  now  brought  into 
shallow,  long  wooden  runs,  where  the  starch  is  deposited, 
the  alkaline  water  running  off.  Finally,  the  starch  is  washed 
with  water,  and  dried  at  a  low  temperature 

Starch  has  a  granular  structure,  the  grains  as  seen  under 
the  microscope  having  a  series  of  concentric  markings,  with  a 
nucleus. 

Starch  in  its  usual  condition  is  insoluble  in  water.  If  ground 
with  cold  water,  it  is  partly  dissolved.  If  heated  with  water, 
the  membranes  of  the  starch-cells  are  broken,  and  the  contents 
form  a  partial  solution.  On  cooling,  it  forms  a  jelly  called 
starch  paste. 

With  iodine,  starch  paste  gives  a  deep  blue  color;  with 
bromine,  a  yellow  color. 

Experiment  42.  Make  some  starch  paste  thus  :  Put  a  few  grammes 
of  starch1  in  an  evaporating  dish;  pour  enough  cold  water  upon  it  to 
cover  it ;  grind  it  under  the  water  with  a  pestle,  and  then  pour  200CC  to 
300CC  hot  water  upon  it.  When  this  is  cool,  add  a  few  drops  to  a  litre 
of  water,  and  then  add  a  few  drops  of  potassium  iodide.  As  long  as 
the  iodine  is  in  combination  with  the  potassium  no  change  of  color 
takes  place ;  but  if  the  iodine  is  set  free  by  the  addition  of  a  drop  or 
two  of  chlorine  water,  or  of  strong  nitric  acid,  the  entire  liquid  turns 
a  beautiful  dark  blue.  The  cause  of  this  color  is  the  formation  of  a 
very  unstable  compound  of  starch  and  iodine.  The  color  is  easily 
destroyed  by  a  slight  excess  of  chlorine  water  (try  it  in  a  test-tube)  ; 
by  alkalies  (try  it) ;  by  sulphurous  acid  (try  it)  ;  by  hydrogen  sulphide 
(try  it)  ;  etc.  It  is  also  destroyed  by  heating.  (Heat  some  of  the 
solution  in  a  test-tube,  and  let  it  stand.)  The  color  reappears  on  cooling. 

Experiment  43.  Use  some  of  the  starch  paste  in  studying  the  effect 
of  bromine  upon  it.  Use  dilute  solutions.  The  bromine  must  be  in  the 
free  condition. 

Starch  is  converted  into  dextrin,  maltose,  and  glucose  by 
dilute  acids;  diastase  converts  it  into  dextrin,  maltose,  and 
isomaltose. 

1  The  purest  form  of  starch  to  be  found  In  the  market  is  that  made  from  arrowroot 
Ordinary  starch  contains  other  substances  which  sometimes  interfere  with  the  reactions. 


204  CARBOHYDRATES 

Experiment  44.  Add  20CC  concentrated  hydrochloric  acid  to  200CC  of 
the  starch  paste  already  made,  and  heat  for  two  hours  on  the  water- 
bath,  connecting  the  flask  with  an  inverted  condenser  (see  Fig.  8). 
Then  examine  with  Fehling's  solution.  Test,  also,  some  of  the  original 
starch  paste  with  Fehling's  solution. 

When  starch  is  treated  for  a  few  days  with  cold,  dilute 
mineral  acids,  it  is  converted  into  "soluble  starch,"  which 
dissolves  in  water  without  the  formation  of  a  paste. 

Starch  is  used  extensively  in  laundries,  as  a  food,  and  in 
making  glucose  (grape  sugar). 

Glycogen,  (C6U.WO5\.  —  This  is  a  carbohydrate  resembling 
starch  that  occurs  in  the  animal  organism.  It  is  found  in 
the  tissues  of  nearly  all  animals  as  a  reserve  material,  but 
disappears  during  exercise  or  hunger.  It  is  especially  abun- 
dant in  the  liver  of  healthy  animals.  It  yields  dextrin. 
maltose,  and  c?-glucose  when  hydrolyzed. 


Dextrin,  CeHioOs.  —  Dextrin  is  formed  by  treating  starch 
with  dilute  acids  or  diastase.  It  is  converted  by  further  treat- 
ment with  acids  into  glucose.  The  substance  ordinarily  called 
dextrin  has  been  shown  to  be  a  mixture  of  several  isomeric  sub- 
stances which  resemble  each  other  very  closely.  The  mixture 
is  an  uncrystallizable  solid.  It  is  strongly  dextro-rotatory, 
gives  a  red  color  with  iodine,  and  does  not  reduce  Fehling's 
solution.  It  is  used  extensively  as  a  substitute  for  gum. 

Gums.  —  Under  this  head  are  included  a  number  of  sub- 
stances which  occur  in  nature.  One  of  the  best  known  is  gum 
arable,  which  is  obtained  in  Senegambia  from  the  bark  of  trees 
belonging  to  the  Acacia  variety.  Its  formula,  like  that  of 
cane  sugar,  is  C12H22On.  Other  gums  are  wood  gum,  obtained 
from  the  birch,  ash,  beech,  etc.  ;  bassorin,  the  chief  constituent 
of  gum  tragacanth,  etc. 

Our  knowledge  of  the  chemistry  of  these  gums  is  very 
limited. 


CHAPTER   XII 

MIXED  COMPOUNDS  CONTAINING  NITROGEN 

IN  speaking  of  the  preparation  of  dibasic  acids  from  mono* 
basic  acids,  reference  was  made  to  cyan-acetic  and  the  two 
cyan-propionic  acids.  These  are  simple  cyanogen  substitution- 
products  analogous  to  chlor-acetic  and  the  two  chlor-propionic 
acids.  They  are  made  by  treating  the  chlorine  products  with 
potassium  cyanide.  They  have  been  useful  chiefly  in  the 
preparation  of  dibasic  acids,  as  described  in  connection  with 
malonic  and  the  two  succinic  acids.  It  will  therefore  not  be 
necessary  to  treat  of  them  individually  here. 

NOTE  FOR  STUDENT.  —  How  can  malonic  be  made  from  acetic  acid; 
and  the  two  succinic  acids  from  propionic  acid?  Give  the  equations. 

The  chief  substances  to  be  considered  under  the  head  of 
mixed  compounds  containing  nitrogen  are  the  amino-acids  and 
the  acid  amides.  As  will  be  seen,  both  these  classes  of  sub- 
stances are  of  special  interest,  as  they  represent  forms  of  com- 
bination which  are  favorite  ones  in  nature,  especially  in  the 
animal  kingdom,  some  of  the  most  important  substances  found 
in  the  animal  body,  such  as  urea,  uric  acid,  glycocoll,  etc.,  be- 
longing to  one  or  both  the  classes. 

AMINO-ACIDS 

The  relation  of  an  amino-acid  to  the  simple  acid  is,  as  the 
name  implies,  the  same  as  that  of  an  amino  derivative  of  a 
hydrocarbon  to  the  hydrocarbon.  That  is  to  say,  it  may  be  re- 
garded as  the  acid  in  which  a  hydrogen  has  been  replaced  by 
the  amino  group,  NH2.  Thus,  amino-acetic  acid  is  represented 

205 


206         MIXED   COMPOUNDS   CONTAINING   NITROGEN 

by  the  formula  CH2<C02H;  while  ainmo-methane,  or  methyl- 

amine,  is  represented  thus:  CH3.NH2.  The  reasons  for  regard- 
ing methyl-amine  as  a  substituted  ammonia  have  been  stated. 
The  formula  is  based  upon  the  reactions  of  the  substance; 
that  is,  upon  its  chemical  conduct  and  the  methods  used  in  its 
preparation.  The  same  arguments  lead  in  the  same  way  to  the 
view  that  the  amino-acids  are  substituted  ammonias,  and,  at 
the  same  time,  acids.  The  simplest  method  for  their  prepara- 
tion consists  in  treating  halogen  derivatives  of  the  acids  with 
ammonia.  Thus  amino-acetic  acid  can  be  made  by  treating 
brom-acetic  acid  with  ammonia:  — 


NOTE  FOR  STUDENT.  —  Compare  this  reaction  with  that  made  use  of 
for  making  methyl-amine. 

NH2 
Ammo-formic  acid,  carbamic  acid,  I          .  —  This  acid 

CO^H 

is   not  known  in  the  free  condition.     Its    ammonium    salt, 
NH2 

I  ,  is   formed  when   carbon   dioxide   and  ammonia   are 

C02NH4 

brought  together,  and  it  is  therefore  contained  in  commercial 
ammonium  carbonate  :  — 


C02  +  2NH3=C02NH4. 

The  other  carbamates  are  prepared  from  the  ammonium 
salt.  They  are  decomposed,  yielding  carbonates  and  ammonia. 
Thus,  when  potassium  carbamate  is  warmed  in  water  solution, 
decomposition  takes  place,  as  represented  in  the  equation,  — 

NH2  ,  C02K  +  H20  =  NH3  +  HKC03. 
The  ethereal  salts  of  carbamic  acid,  called  urethanes,  are 


GLYCOCOLL  207 

readily  made  by  treating  the  ethereal  salts  of  chlor-f  ormic  acid 
(see  p.  158)  with  ammonia  :  — 

Cl  NH2 

I  I 

C02C2H5  +  2  NH3  =  C02C2H5  +  NH4C1. 

Amino-formic  acid  cannot  be  taken  as  a  fair  representative 
of  the  amino-acids,  any  more  than  carbonic  acid  can  be  taken 
as  a  fair  representative  of  the  hydroxy-acids. 

Glycocoll,  glycine, 


Tn 
amino-acetic  acid  '  ~ 


,] 
j 

bile  are  contained  two  complicated  acids,  which  are  known  as 
glycocholic  and  taurocholic  acids.  When  glycocholic  acid  is 
boiled  with  hydrochloric  acid,  it  breaks  up,  yielding  cholic  acid 
and  glycocoll.  In  the  urine  of  horses  is  found  an  acid  known 
as  hippuric  acid.  When  this  is  boiled  with  hydrochloric  acid, 
it  breaks  up  into  benzoic  acid  and  glycocoll. 

When  uric  acid  is  treated  with  hydriodic  acid,  glycocoll  is 
one  of  the  products.  Further,  glycocoll  is  formed  when  glue  is 
boiled  with  baryta  water  or  dilute  sulphuric  acid.  Its  forma- 
tion from  brom-acetic  acid  and  ammonia,  mentioned  above,  gives 
the  clearest  indication  in  regard  to  its  relation  to  acetic  acid. 

Amino-acetic  acid  is  soluble  in  water,  insoluble  in  alcohol  or 
ether.  It  has  a  sweetish  taste,  and  is  sometimes  called  gelatin 
sugar. 

Amino-acetic  acid  has  both  acid  and  basic  properties.  It 
unites  with  acids,  forming  weak  salts  ;  and  it  acts  upon  bases, 
giving  salts  with  metals,  —  the  amino-acetates.  It  also  unitea 
with  salts,  forming  double  compounds. 

Examples  of  the  compounds  with  acids  are  the 

.    HC1 


7-7-7  77  •   7  /^TT 

Hydrochloride  ....     CH2  < 

2 

,  .,      __.  __.       NH2.HN03 

and.  the  Nitrate     ......    CH2<^^.:T  , 

C(J2Jl 

of  the  salts  with  metals, 


208         MIXED   COMPOUNDS   CONTAINING   NITROGEN 

Zinc  ammo-acetate  .  .  Zn(C2H4N02)2-f-H2O, 
and  Copper  amino-acetate  .  Cu(C2H4N02)2  +  H20  ; 
of  the  compounds  with  salts,  the  double  salt  of 

Copper  nitrate  j  . 

and  Copper  ammo-acetate,  \      v 

Treated  with  nitrous  acid,  glycocoll  is  converted  into  hydroxy- 
acetic  acid.  With  soda-lime  it  gives  inethyl-amine. 

NOTE  FOR  STUDENT.  —  Write  the  equation  representing  the  reaction 
that  takes  place  when  glycocoll  is  treated  with  nitrous  acid. 

It  seems  probable  that  amino-acetic  acid  and  other  similar 
compounds  are  really  salts  formed  by  the  union  of  the  acid  con- 
stituent, carboxyl,  with  the  basic  constituent,  NH2.  In  accord- 
ance with  this  view  the  formula  should  be  written  thus  :  — 


Sarcosine,    methyl-glyoocoll,   C3H7NO2(cH2<Q^HCHil, 
NH2.CH, 

or  CH2\        /O     )•  —  When  brom-ace  tic  acid  is  treated  with 
CO 

methyl-amine  instead  of  with  ammonia,  a  reaction  takes  place 
similar  to  that  which  takes  place  with  ammonia,  the  product 
being  methyl-glycocoll  or  sar  cosine  :  — 


CH2  <       H  +  2  CH3  .  NH2  =  CH2  <  3  +  KH3(CH8)Br. 

Sarcosine 

Sarcosine  is  a  product  of  the  decomposition  of  creatine,  which 
is  found  in  flesh,  and  of  caffeine,  which  is  a  constituent  of 
coffee  and  tea.  It  is  obtained  from  creatine  and  caffeine  by 
boiling  them  with  baryta  water.  Its  properties  are  much  like 
those  of  glycocoll. 

Amino-propionic  acids,  OSH7NO2.  —  These  acids  bear  to 
propionic  acid  relations  similar  to  that  which  amino-acetic  acid 


CYSTINE  209 

bears  to  acetic  acid.  There  are  two,  corresponding  to  a-  and 
/3-chlor-propionic  acids,  from  which  they  are  made.  Their 
properties  are  much  like  those  of  glycocoll.  a-Amino-propionic 
acid,  which  is  also  called  alanine,  is  widely  distributed  in  nature. 
Among  the  amino  derivatives  of  the  higher  members  of  the 
fatty  acid  series,  two  are  of  special  importance.  These  are 
leucine  and  isoleucine. 

Leucine,  ?-a-aminoisobutylacetic  acid, 

|^3  >  CH  .  CH2  .  CH(NH2)  .  COOH, 
bJti3 

is  a  frequent  product  of  decomposition  of  vegetable  and 
animal  albuminoid  substances.  The  inactive  variety  has 
been  made  artificially  by  starting  with  isovaleric  aldehyde, 

CH 

3  >  CH  .  CH2  .  CHO,  and  by  means  of  hydrocyanic  acid  convert- 
CH3 

ing  this  into  the  amino  acid  of  the  above  formula.  When  this 
inactive  acid  is  split  into  its  optically  active  components,  the 
levo  variety  is  found  to  be  identical  with  the  leucine  obtained 
from  natural  sources. 


Isoleucine,   d-a-amino-/^methyl-/^ethyl-propionic   acid, 
>CH.CH(NH2)  .COOH,  like  leucine,  is  a  frequent  prod- 


f  TT     f^TT 

3>      2 


CH3 

uct  of  decomposition  of  vegetable  and  animal  albuminoid  sub- 
stances.    It  is  dextro-rotatory. 

Serine,  which  is  obtained  from  silk  by  boiling  with  dilute 
acids,  has  been  shown  to  be  a-amino-/3-hydroxy-propionic  acid, 
CH2(OH)  .  CH(NH2)  .  COOH. 

Cystine,  C6H12N204S2,  a  substance  that  is  sometimes  found 
as  a  crystalline  sediment  in  the  urine  of  human  beings  and 
dogs,  is  a  derivative  of  a-amino-propionic  acid.  Tin  and 
hydrochloric  acid  reduce  it  to  cystein,  C3H7N02S.  The  two 


210         MIXED    COMPOUNDS  CONTAINING   NITROGEN 

substances  bear  to  each  other  the  relation  represented  by  these 
formulas :  — 

CH2.SH  CH2.S S.H2C 

I  I                             I 

CH .  NH2  CH .  NH2  H2N .  HC 

I  I                             I 

COOH  COOH          HOOC 

Cysteln  Cystine 


AMINO-SULPHONIC  ACIDS 

Just  as  there  are  amino  derivatives  of  the  carboxyl  acids, 
so,  too,  there  are  amino  derivatives  of  the  sulphonic  acids. 
The  most  important  of  these  is 

Taurine,  )  p  /  SO3H\ 

£-Amino-ethyl-sulphonic  acid,  )    2    ?JN  'U\  NH2  / 

Taurine  is  found  in  combination  with  cholic  acid  in  taurocholic 
acid,  in  ox  bile,  and  the  bile  of  many  animals,  as  well  as  in 
other  animal  liquids.  It  has  been  made  synthetically  from 

OTT 

isethionic  acid,  C2H4<go  H,  by  treating  the  acid  successively 
with  phosphorus  pentachloride  and  ammonia  :  — 


Isethionic  acid  Chlor-ethyl-sulphon-chloride 


Chlor-ethyl-sulphonic  acid 


Taurine 


Taurine  crystallizes  in  large  monoclinic  prisms.     It  is  a  very 
stable  substance,  and  can  be  boiled  with  concentrated  acids 


ACID   AMIDES  211 

without  decomposition.     With  nitrous  acid  it  yields  isethionic 
acid. 

It  unites  with  strong  bases  forming  salts,  but  not  with  acids. 
This  is  in  accordance  with  the  view  that  taurine  is  an  inner 

ammonium  salt  as  represented  by  the  formula  C2H4<G«  3>O. 

DU2 

AMINO-DIBASIC  ACIDS 

Aspartic  acid,  I  n  TT  i^n  fr  TT  rxrTT  \  ^  C02H 

Amino-succinic  acid,  \  C4H7NO4(C2H3(*  H2)  < 


or  H02C  .  H2C  -  CH(NH2)  .  C02H. 

Aspartic  acid  occurs  in  pumpkin  seeds,  and  is  frequently 
met  with  as  a  product  of  boiling  various  natural  compounds 
with  dilute  acids.  Thus,  for  example,  it  is  formed  when  casein 
and  albumin  are  treated  in  this  way.  It  is  formed  also  when 
asparagine  (which  see)  is  boiled  with  acids  or  alkalies. 

Aspartic  acid  crystallizes  in  rhombic  prisms,  which  are  diffi- 
cultly soluble  in  water.  .The  boiling  solution  of  the  natural 
product  is  levo-rotatory.  A  cold  solution  is  dextro-rotatory. 
It  contains  an  asymmetric  carbon  atom,  and  the  three  varieties 
(d-,  1-,  and  i-)  suggested  by  the  theory  are  known.  When 
treated  with  nitrous  acid,  each  is  converted  into  the  corre- 
sponding malic  acid. 

ACID  AMIDES 

When  the  ammonium  salt  of  acetic  acid  is  heated,  it  gives  off 
water,  and  a  body  distils  over  which  is  known  as  acetamide, 
The  reaction  is  represented  by  the  following  equation  :  — 

CH3  .  COONH4  =  CH3  .  CONH2  +  H20. 

The  substance  obtained  has  neither  acid  nor  basic  properties. 
An  examination  of  the  ammonium  salts  of  other  acids  that 
contain  carboxyl  shows  that  the  reaction  is  a  general  one,  and 
a  class  of  neutral  bodies,  known  as  the  acid  amides,  can  thus 
be  obtained.  As  no  one  of  the  acid  amides  of  the  fatty  acid 


212         MIXED  COMPOUNDS   CONTAINING   NITROGEN 

series  is  of  special  importance,  a  few  words  of  a  general  char- 
acter in  regard  to  the  class  will  suffice. 

Besides  the  reaction  above  given,  there  are  two  others  of 
general  application  for  the  preparation  of  the  acid  amides. 
One  consists  in  treating  an  ethereal  salt  of  an  acid  with  am- 
monia; thus,  when  ethyl  acetate  is  treated  with  ammonia,  this 
reaction  takes  place :  — 

CH3 .  C02C2H5  +  NH3  =  CH3 .  CONH2  +  C2H60. 

The  other  reaction  consists  in  treating  the  acid  chlorides  with 
ammonia.  Thus,  to  get  acetamide,  we  may  treat  acetyl  chloride 
(see  p.  62)  with  ammonia :  — 

CH3 .  COC1  +  2  NH3  =  CH3.  CONH2  +  NH4C1. 

This  last  reaction  is  perhaps  most  frequently  used.  It  shows 
the  relation  that  exists  between  acetic  acid  and  acetamide. 
For  acetyl  chloride  is  made  from  acetic  acid  by  treatment  with 
phosphorus  trichloride,  and  is,  therefore,  as  has  been  pointed 
out,  to  be  regarded  as  acetic  acid  in  which  the  hydroxyl  is 
replaced  by  chlorine.  Now,  by  treatment  with  ammonia  the 
same  reaction  takes  place  as  that  which  we  have  had  to  deal 
with  in  the  preparation  of  amino-acids ;  the  chlorine  is  replaced 
by  the  amino  group.  Therefore,  acetamide  is  acetic  acid  in 
which  the  hydroxyl  is  replaced  by  the  amino  group,  as  shown 
in  the  formulas :  — 

0  0 

II  II 

CH3.  C  -  OH  CH3  -  C  -  NH2. 

Acetic  acid  Acetamide 

As  the  acid  hydrogen  of  the  acid  is  replaced,  the  amide  is  not 
an  acid.  On  the  other  hand,  the  basic  properties  of  the 
ammonia  are  destroyed  by  the  presence  of  the  acid  residue  as 
a  part  of  its  composition.  This  latter  fact  may  be  stated  in 
another  way  j  viz.,  when  an  ammonia  residue  is  in  combination 


ACID   AMIDES  213 

with  carbon,  which  in  turn  is  in  combination  with  oxygen,  its 
basic  properties  are  destroyed. 

The  amides  are  converted  into  ammonia  and  a  salt  when 
boiled  with  strong  bases  :  — 

CH3.  CONH2  +  KOH  =  CH3C02K  +  NH3. 

They  are  converted  into  cyanides  by  treatment  with  phos- 
phorus pentoxide,  P205:  — 

CH3  .  CONH2  =  CH3  .  CK  +  H20. 

As  the  substance  obtained  in  this  way  is  identical  with  methyl 
cyanide,  which  is  formed  by  heating  the  potassium  salt  of 
methyl-sulphuric  acid  with  potassium  cyanide,  the  reaction 
furnishes  additional  evidence  in  favor  of  the  conclusion 
that  in  the  cyanides  the  carbon  and  not  the  nitrogen  of  the 
cyanogen  group  is  in  combination  with  the  hydrocarbon  residue, 
as  represented  in  the  formula  CH3—  C  —  N. 

As  the  amide  can  be  made  from  the  ammonium  salt,  and 
the  cyanide  or  nitrile  from  the  amide,  so,  by  starting  with  the 
cyanide,  the  amide  and  the  ammonium  salt  can  be  made.  The 
reaction  by  which  the  cyanides  are  converted  into  acids  is 
based  upon  these  relations  :  — 


B,  .  COONH4->R  .  CONH2->K  .  CN, 
and 


As  acetamide  is  made  by  treating  ammonia  with  the  chloride 
of  acetic  acid,  so,  by  treating  ammonia  with  the  chloride  of  any 
acid,  the  corresponding  amide  can  be  made.  Similarly,  by 
treating  acid  amides  with  acid  chlorides,  more  complicated  com- 
pounds can  be  obtained.  Of  these  di-acetamide,  NH(C2H30)2, 
and  tri-acetamide,  N(C2H30)3,  may  serve  as  examples.  The  re- 
lations of  these  substances  to  ammonia  and  to  acetic  acid  are 
shown  by  the  formulas,  ordinary  or  .  mon-acetamide  being 
NH2.C2H30  or  CH3.CO.NH3. 


214         MIXED   COMPOUNDS   CONTAINING   NITROGEN 

The  preparation  of  an  acid  amide  by  treating  an  ester  with 
ammonia  is  well  illustrated  by  Experiment  45,  in  which  ethyl 
oxalate  is  first  prepared  and  this  then  converted  into  oxarnide 
by  treating  it  with  aqueous  ammonia :  — 

COOH       C2H5OH       COOC2H5 

I  +  =|  +2H20. 

COOH       C2H5OH       COOC2H2 

Oxalic  acid  Alcohol  Ethyl  oxalate 

COOC2H5       NH3       COKH2 

[  +  =1  +2  C2H5OH. 

COOC2H5       NH3       CONH2 

Ethyl  oxalate  Oxamide 

Experiment  45.  Into  a  mixture  of  50s  oxalic  acid  (dehydrated  at 
100°)  and  75s  absolute  alcohol  pass  dry  hydrochloric  acid  gas.  The  mix- 
ture becomes  warm.  Cool  by  placing  the  vessel  in  ice-water  and  continue 
the  passage  of  the  hydrochloric  acid  at  this  temperature  to  saturation. 
Then  let  stand  overnight.  Now  pour  the  product  into  a  mixture  of 
crushed  ice  and  finely  powdered  crystallized  sodium  carbonate,  stirring 
continually,  and  taking  care  that  the  mass  remains  cold  and  alkaline. 
Wash  the  ester  with  a  little  water. 

Dissolve  some  of  the  ester  in  alcohol  and  add  strong  ammonia.  Filter 
off  the  precipitate,  which  is  oxamide,  and  wash  with  water.  See  whether 
it  conducts  itself  like  an  acid.  Has  it  an  acid  reaction  ?  Boil  with  dilute 
potassium  hydroxide  and  notice  whether  ammonia  is  given  off.  Why 
does  it  dissolve.  How  can  the  oxalic  acid  be  extracted  from  the  solution  ? 

When  oxamide  is  treated  with  a  dehydrating  agent,  such  as  phosphorus 
pentoxide,  it  is  converted  into  cyanogen  : 

CONH2         CN 
|  ->    I      +  2  H20. 

CONH2         CN 

Hofmann's  reaction.  —  When  an  acid  amide  is  treated 
with  sodium  hydroxide  and  bromine,  three  reactions  take  place, 
as  represented  in  the  equations :  — 

CH3.CO£TH2-{-Br2  =  CH3.CONHBr  +  HBr; 
CH3.  CONHBr  +  NaOH  =  CH3N  :  C  :  0  +  NaBr  +  H20 ; 
CH3.  N :  C  :  0  +  H20  =  CH3NH2  +  C02. 


ASPARAGINE  215 

It  is  thus  possible  by  starting  with  any  acid  to  pass  to  the 
primary  amine  containing  the  same  radical  as  the  acid.  In  the 
case  of  acetic  acid  the  three  stages  are  represented  below :  — 


CH3. 

Acetic  acid  Acetamide  Methylamine 

This  reaction  has  become  of  great  practical  importance  in 
connection  with  the  artificial  preparation  of  indigo  (which  see). 

Amic  acids.  —  When  the  amide  of  a  polybasic  acid  is  boiled 
with  ammonia,  and  under  some  other  circumstances,  partial  de- 
composition takes  place,  and  a  substance  is  formed  which  is 
both  amide  and  acid.  Thus,  in  the  case  of  oxamide,  the  prod- 

C02H 
uct  is  oxamic  acid,  \         .    This  acid  forms  well-characterized 

CONH2 

salts  and  other  derivatives  such  as  are  obtained  from  acids  in 
general.  There  is  one  acid  of  this  kind  which  is  a  well-known 
natural  substance.  It  has  already  been  referred  to  in  connec- 
tion with  aspartic  acid,  which  is  closely  related  to  it.  It  is 

Asparagine,  amino-succinamic  acid, 

/CH2.CONH2         \ 
C4H8N2O3  +  ELO    I  . — Asparagine  is  found 

VCH(NH2).COOH/ 

in  many  plants,  as  in  asparagus,  liquorice,  beets,  peas,  beans, 
vetches,  and  in  wheat.  It  can  be  made  by  treating  mon-ethyl 
amino-succinate  with  ammonia. 

NOTE  FOR  STUDENT.  —  What  reaction  takes  place  ?  Write  the  equa- 
tion. 

Asparagine  forms  large  rhombic  crystals,  difficultly  soluble  in 
cold  water,  more  easily  in  hot  water.  When  boiled  with  acids 
or  alkalies,  it  is  converted  into  aspartic  acid  and  ammonia. 

NOTE  FOR  STUDENT.  —  Notice  that  only  the  amino  group  of  the  amide 
is  driven  out  of  the  compound  by  this  treatment.  The  other  amino 
group  which  is  contained  in  the  hydrocarbon  portion  of  the  compound 
is  not  affected. 


216          MIXED   COMPOUNDS   CONTAINING   NITROGEN 

Nitrous  acid  converts  asparagine  into  malic  acid. 

Asparagine  contains  an  asymmetric  carbon  atom,  and 
the  two  theoretically  possible  stereoisomeric  varieties  are 
known.  The  levo-rotatory  variety  is  found  in  the  seeds  of 
many  plants,  in  asparagus,  in  beets,  in  peas,  beans,  and  in 
vetch  sprouts.  The  dextro  variety  is  also  found  in  vetch 
sprouts. 

/TV 

Succinimide,  C2H4  <  ~Q  >  NH. — This  compound  deserves 

attention  in  this  connection,  as  it  represents  a  not  uncommon 
class  known  as  the  add  imides.  They  are  formed  from  poly- 
basic  acids,  most  simply  from  dibasic  acids.  They  may  be 
regarded  as  the  anhydrides  in  which  the  imino  group  has 
been  substituted  for  an  oxygen  atom.  They  are  formed  from 
the  aoiides  by  loss  of  ammonia.  Thus :  — 

CH2.CONH2     CH2.C(X 
I  =  |  >NH  + NH8. 

CH2.CONH2     CH2.C(K 

Succinamide  Succinimide 

The  hydrogen  atom  of  the  imide  is  replaceable  by  some 
inetals,  or  the  imide  has  the  properties  of  a  weak  acid. 

Cyan-amides,  CN2H2.  —  In  treating  of  cyanic  acid,  the 
existence  of  two  chlorides  of  cyanogen  was  mentioned :  one, 
a,  liquid  having  the  formula  NCC1 ;  the  other,  a  solid  of  the 
formula  NsCgCLj.  When  the  former  is  treated  with  ammonia, 
it  is  converted  into  an  amide,  NO .  NH2,  which  bears  to  cy- 
anic acid,  NO  .  OH,  the  relation  of  an  amide.  Like  the  other 
simple  compounds  of  cyanogen,  cyan-amide  readily  undergoes 
change.  Heated  to  150°  or  when  allowed  to  stand,  it  is  con- 
verted into  di-cyan-diamide,  C2K4H4;  while,  when  heated  to 
above  150°,  a  violent  reaction  takes  place,  and  tri-cyan- 
triamide,  C3N6H6,  is  formed.  The  latter  compound  is  also 
called  melamine  and  cyanuramide,  and  from  certain  methods 
of  formation  it  is  concluded  that  it  is  the  amide  of  cyanuric 


CREATINE  217 

acid.  It  is  a  strong  mon-acid  base.  The  formation  of  these 
compounds  is  particularly  interesting,  as  illustrating  the 
tendency  on  the  part  of  the  simpler  cyanides  to  undergo 
polymerization. 

Calcium  cyanamide,  CN2Ca.  —  This  compound  has  come 
into  prominence  as  a  fertilizer.  It  furnishes  the  nitrogen 
necessary  to  the  growth  of  plants.  It  is  made  by  passing 
nitrogen  over  calcium  carbide  heated  to  750°-1000°  in  an 
electric  furnace,  when  the  reaction  represented  in  this  equation 
takes  place:  — 


The  nitrogen  used  is  obtained  by  fractional   distillation  of 
liquid  air. 

Guanidine,  CN3H5.  —  This  substance,  which  is  closely 
related  to  cyan-amide,  is  formed  by  the  oxidation  of  guanine 
(which  see),  and  this  in  turn  is  obtained  from  guano.  It  can 
also  be  made  by  treating  cyanogen  iodide  with  ammonia  :  — 


the  product  being  the  hydriodic  acid  salt  of  guanidine.     As 
will  be  seen,  guanidine  is  cyan-amide  plus  ammonia  :  — 


It  is  a  strongly  alkaline  base.     Boiled  with  dilute  sulphuric 
acid  or  baryta  water,  it  yields  urea  and  ammonia  :  — 

CN3H5  +  H20  =  CON2H4  +  NH3. 

Guanidine  Urea 

Creatine,  CJIJ$3O2.  —  This  substance  is  found  in  the 
muscles  of  all  animals.  •  It  is  closely  related  to  guanidine 
and  also  to  sarcosine  (see  p.  208).  It  has  been  made  syn- 
thetically by  bringing  cyan-amide  and  sarcosine  together, 


218         MIXED   COMPOUNDS   CONTAINING   NITROGEN 

--•*   • 

The  reaction  is  analogous  to  that  made  use  of  for  the  prepara- 
tion of  guanidine :  — 

HN.CH3  /NH2 

JN  =  \j  —  J\  -tl2  ~r~  — —  -tlJN  :  Ly  c  /^TT    r^r^r^TT 

H/S    rir\  TT  vKT  ^  v»**f»  vA/VJuu 

2O.CO2M  NJN  <        * 

O±13 

Cyan-amide  Sarcosine  Creatine 

Creatinine,  C4H7N3O,  is  in  small  quantity  a  constant  con- 
stituent of  urine.  It  can  be  made  from  creatine  by  evap- 
orating its  solutions,  especially  if  acids  are  present.  In 
contact  with  alkalies  it  gradually  takes  up  the  elements  of 
water  and  forms  creatine.  It  is  a  strong  base,  forming  with 
acids  well-crystallized  salts.  Its  relation  to  creatine  is  repre- 
sented thus: — 


CH2.COOH  \N   .CH2 .    0. 

CH3  ^ 

Creatine  Creatinine 


Urea,  or  carbamide,  and  derivatives. — Closely  related 
to  the  nitrogen  compounds  just  considered  is  urea,  or  the 
amide  of  carbonic  acid.  Its  importance  and  certain  peculiari- 
ties distinguish  it  from  the  other  acid  amides,  and  it  is  there- 
fore treated  of  by  itself. 

Urea  is  found  in  the  urine  and  blood  of  all  mammals,  and 
particularly  in  the  urine  of  carnivorous  animals.  Human 
urine  contains  from  2  to  3  per  cent ;  the  quantity  given  off  by 
an  adult  man  in  24  hours  being  about  30g.  Urea  can  be  made 
by  the  following  methods:  — 

(1)   By  treating  carbonyl  chloride  with  ammonia :  — 

COC12  +  4  NH3  =  CON2H4  +  2  JSTH4C1. 
(What  is  the  analogous  reaction  for  the  preparation  of  acetamide  ?) 


UREA  219 


(2)   By  heating  ammonium  carbamate  :  — 

CO  <  =  C0^H4  +  2  H20. 


(3)    By  treating  ethyl  carbonate  with  ammonia  :  — 

OP  TT 
C0<  ™*      +  2  NH3  =  CON2H4  +  2  C2H60. 


(What  is  the  analogous  reaction  for  preparing  oxamide  ?) 

(4)  By  the  addition  of  water  to  cyan-amide  :  — 

CN  .  NH2  +  H20  =  C01Sr2H4. 

(5)  By  evaporation  of  ammonium  cyanate  in  aqueous  solu- 
tion :  — 

=  CON2H4. 


This  reaction  is  of  special  interest,  for  the  reason  that  it  is  the 
first  example  of  the  formation,  by  artificial  methods  from  in- 
organic substances,  of  an  organic  compound  found  in  the  ani- 
mal body  (see  p.  1). 

Urea  is  most  readily  obtained  from  urine. 

Experiment  46.  Evaporate  four  or  five  litres  fresh  urine  to  a  thin, 
syrupy  consistence.  After  cooling  add  ordinary  concentrated  nitric  acid, 
when  crystals  of  urea  nitrate  are  obtained.  Filter,  wash,  and  recrys- 
tallize  from  moderately  concentrated  nitric  acid.  When  the  crystals  of 
urea  nitrate  are  white,  dissolve  again  in  water,  and  add  finely-powdered 
barium  carbonate.  The  nitric  acid  forms  barium  nitrate,  and  the  urea  is 
left  in  free  condition.  Evaporate  to  dryness,  and  from  the  residue  extract 
the  urea  with  strong  alcohol. 

Experiment  47.  Weigh  the  potassium  cyanate  obtained  in  Experi- 
ment 26,  p.  85.  Dissolve  in  cold  water,  and  to  this  add  a  solution  of 
ammonium  sulphate  containing  the  sulphate  in  the  proportion  of  one 
molecule  to  two  molecules  of  the  cyanate.  Evaporate  to  a  small  volume, 
and  allow  to  cool.  Potassium  sulphate  will  crystallize  out.  Filter  this 
off,  and  evaporate  to  dryness.  Extract  with  alcohol.  The  urea  will 
crystallize  from  the  alcoholic  solution  when  it  is  brought  to  proper  con- 
centration. Give  all  the  reactions  involved  in  passing  from  potassium 


220         MIXED   COMPOUNDS   CONTAINING  NITROGEN 

ferrocyanide  to  urea.  Compare  the  urea  made  artificially  with  that  made 
from  urine. 

Urea  crystallizes  from  alcohol  in  large,  rhombic  prisms, 
which  melt  at  132°. 

Experiment  48.  Determine  the  melting-points  of  both  the  natural 
and  artificial  specimens  of  urea. 

Urea  is  easily  soluble  in  water  and  alcohol.  Heated  with 
water  in  a  sealed  tube  to  180°,  or  boiled  with  dilute  acid  or 
alkalies,  it  breaks  up  into  carbon  dioxide  and  ammonia :  — 

CON2H4  +  H20  =  C02  +  2  NH3. 

The  same  decomposition  of  the  urea  takes  place  spontaneously 
when  urine  is  allowed  to  stand.  Hence  the  odor  of  ammonia, 
is  always  noticed  in  the  neighborhood  of  urinals  that  are  not 
kept  thoroughly  clean.  This  decomposition  is  due  to  the  action 
of  an  organism  known  as  micrococcus  ureas.  This  change  is  a 
good  example  of  the  way  in  which  nature  converts  useless 
material  into  useful  ones.  Urea  is  a  waste-product  of  the  life- 
process.  After  it  has  left  the  body  it  ceases  to  be  of  value, 
whereas  carbon  dioxide  and  ammonia  are  essential  to  the  life 
of  plants. 

Sodium  hypochlorite  or  hypobromite  decomposes  urea  into 
carbon  dioxide,  nitrogen,  and  water :  — 

CO(N2H4)  +  3  NaOCl  =  C02  +  3  NaCl  +  N2  +  2  H20. 

The  carbon  dioxide  is  absorbed  by  the  solution  which  contains 
sodium  hydroxide,  and  the  nitrogen  may  then  be  measured. 
From  the  volume  of  nitrogen  obtained  the  amount  of  urea  can 
be  calculated.  This  is  the  basis  of  one  of  the  methods  used  for 
estimating  urea. 

Experiment  49.  To  a  solution  of  20s  sodium  hydroxide  in  100CO 
water  add  about  5CC  bromine,  and  shake  well.  Make  a  solution  of  urea 
in  water,  and  add  this  to  the  solution  of  the  hypobromite.  An  evolution 
of  gas  will  be  noticed,  showing  that  the  urea  is  decomposed. 


SUBSTITUTED   UREAS  221 

Nitrous  acid  acts  in  a  similar  way :  — 

CON2H4  +  2  HN02  =  C02  +  2  N2  4-  3  H20. 

When  heated,  urea  loses  ammonia,  and  yields  first  biuret 
and  finally  cyanuric  acid  (see  p.  86) :  — 


Urea 

3  CO(NH2)2  =  C3H303N 

Cyanuric  acid 

Biuret  in  alkaline  solution  gives  a  beautiful  violet-red  reaction 
with  a  little  copper  sulphate.  This  biuret-reaction  is  charac- 
teristic of  the  more  complicated  polypeptides  (which  see). 

Urea  unites  with  acids,  bases,  and  salts.     The  hydrogen  of 
the  amino  groups  can  be  replaced  by  acid  or  alcohol  radicals, 

~W  TT       f\     TT     /~\ 

giving  compounds  of  which   acetyl  urea,  C0<^    '        3  ,  and 


NHC1  IT 

ethyl-urea,  CO  <  NH  2   5,  are  examples. 

Among  the  compounds  with  acids,  the  following  may  be 
mentioned:  urea  Jiydrochloride,  CH4N2O.HC1;  urea  nitrate, 
CH4N2O.HN03;  and  urea  phosphate,  CH4N20  .  H3P04.  With 
metals  it  forms  such  compounds  as  that  with  mercuric  oxide, 
2HgO.CH4N20;  with  silver,  CH2N2O.Ag2,  etc.  With  salts  it 
forms  such  compounds  as  2  CO(NH2)2  .  Hg(N03)2  .  3  HgO,  etc. 

Substituted  ureas  —  that  is,  those  derivatives  of  urea 
which  contain  hydrocarbon  residues  in  place  of  one  or  all  the 
hydrogen  atoms  —  can  be  made  from  the  cyanates  of  substi- 
tuted ammonias.  The  fundamental  reaction  is  the  spontaneous 
transformation  of  ammonium  cyanate  into  urea  :  — 


222         MIXED    COMPOUNDS    CONTAINING   NITROGEN 

In  the  same  way,  cyanates  of   substituted   ammonias  are 
transformed  into  substituted  ureas:  — 


CN  .  ONH3C2H5  =  CO  < 
CN  .  ONH2(C2H5)2  =  CO  <        25      etc. 


The  urea  derivatives  which  contain  acid  radicals  are  made 
by  treating  urea  with  the  acid  chlorides:  — 


CO  <        2  +  C2H3OC1  =  CO  <          C2Hs°  +  HC1. 


Acetyl-urea 

NOTE   FOR   STUDENT.  —  In   what  sense   is  acetyl-urea    analogous  to 
acetamide  ? 


Ureids  are  compounds  derived  from  urea  by  the  substitution 
of  acid  residues  for  one  or  more  of  the  hydrogen  atoms.     Thus, 

acetyl-urea,  OC  <         '  3,  is  a  simple  ureid.     The  rela- 


tion between  the  acid  and  urea  in  the  ureid  is  like  that  between 
the  acid  and  ammonia  in  the  amide  :  — 


CH3.  COOH  +  HH2N  =  CH3.  CONH2  +  H20  ; 

Acid  Amide 

CH3.  COOH  +  HHK  CH3.  COHN 

H2N>(  H2N>     )  +  H2°- 

Acid  Urea  Ureid 

The  ureids  of  dibasic  acids  resemble  in  the  same  way  the 
amides  of  these  acids.  One  urea  residue  takes  the  place  of 
the  two  acid  hydroxyls.  Thus,  in  the  case  of  oxalic  acid  the 
relation  is  shown  by  the  formulas  below  :  — 

COOH  +  HHK  CO.KN, 

|  >CO=   |  >CO  +  2H20. 

COOH  +  HHN/  CO.HN/ 

Oxalic  acid          Urea  Ureid  of  oxalic  acid 


BARBITURIC   ACID  223 

There    are    several   compounds   of  this   kind  that  are   of 
importance :  — 


Parabanic  acid,  j 
Oxalyl-urea,          \  C3H2N203 
Oxal-ureid, 


CO.HX 


j\j  •  a-L-Li  v 

I  >CO 

!O    TITtf/ 


CO.HN 


—  This   is 


formed  by  boiling  uric  acid  with  strong  nitric  acid  and  with 
other  oxidizing  agents,  and  by  treating  a  mixture  of  oxalic  acid 
and  urea  with  phosphorus  oxychloride.  It  acts  like  an  acid, 
the  hydrogen  of  the  imide  group  being  replaceable  by  metals, 
as  in  succinirnide.  Its  salts  readily  pass  over  into  salts  of 
oxaluric  acid  when  treated  with  water :  — 

CO.H:N\  COOH 

|  >CO  +  H20  =  I 

CO.HN/  CO.HN.CONH2 

/CO .  OH  \ 

i  ) 

Oxaluric   acid,    C3H4N2OACO .  HN .  CO .  NH2  / ,  bears  to 

parabanic  acid  the  same  relation  that  oxamic  acid  bears  to 
oxamide.  It  occurs  in  the  form  of  the  ammonium  salt  in  small 
quantity  in  human  urine.  With  phosphorus  oxychloride  it 
gives  parabanic  acid. 


Barbituric  acid,  malonyl-urea, 

04H4N  A  +  2  H20    CH2  <        '         >  °°    '   like   Parabanic 


NH 

acid,  is  obtained  from  uric  acid.  It  has  been  made  artificially 
by  treating  a  mixture  of  malonic  acid  and  urea  with  phosphorus 
oxychloride.  Treated  with  an  alkali,  it  breaks  up  into  malonic 
acid  and  urea. 


Diethylbarbituric  acid,  C(C2H5)2<  Q'NH  >C°'  made 
by  the  action  of  the  diethyl  ester  of  diethylmalonic  acid  upon 
urea,  is  an  excellent  soporific.  It  is  known  as  veronal. 


224         MIXED    COMPOUNDS    CONTAINING    NITKOGEN 

Sulphourea,  thio-urea,  CS(NH2)2.  —  This  substance  is 
formed  by  heating  ammonium  sulpho-cyanate,  the  reaction 
being  analogous  to  that  by  which  urea  is  formed  from  am- 
monium cyanate  :  — 


It  forms  rhombic  prisms  melting  at  172°.  It  combines  with 
one  equivalent  of  acids,  forming  salts. 

A  number  of  derivatives  of  sulpho-urea  have  been  made. 
They  resemble  those  obtained  from  urea. 

One  acid,  C5H4N4O3.  —  Uric  acid  occurs  in  human  urine 
in  small  quantity,  in  the  urine  of  carnivorous  animals,  and  in 
the  excrement  of  birds  and  of  reptiles.  The  excrement  of 
reptiles  consists  almost  wholly  of  ammonium  urate.  In  gout, 
uric  acid  is  deposited  in  the  joints,  under  the  skin,  and  in  the 
bladder  as  calculi,  in  the  form  of  insoluble  acid  salts. 

Uric  acid  forms  colorless,  crystalline  scales,  and  is  almost 
insoluble  in  water.  It  acts  like  a  weak  dibasic  acid. 

By  treating  the  lead  salt  of  uric  acid  with  methyl  iodide, 
two  isomeric  methyl-uric  acids  can  be  obtained,  arid  these  can 
be  further  converted  into  a  tetra-methyl-uric  acid,  which  is 
derived  from  uric  acid  by  the  substitution  of  four  methyl 
groups  for  the  four  hydrogen  atoms,  C^CHg^lS^Og.  When 
this  is  decomposed,  all  the  methyl  groups  are  given  off  in 
combination  with  nitrogen  in  the  form  of  methyl-amine.  This 
shows  that  uric  acid  contains  four  imino  groups,  as  shown  in 
the  formula  C5(NH)403.  Other  transformations  show  that  the 
constitution  of  the  acid  must  be  represented  by  the  formula 

NH-CO 
I          I 
CO       C-NH. 

>CO. 
/ 


According  to  this,  uric  acid  contains  two  urea  residues  com« 


XANTHINE  225 

CO 

bined  in  different  ways  with  the  group  C  .     It  is  to  be  re- 

II 
C 

garded  as  a  diureid  of  a  hypothetical  trihydroxyacrylic  acid, 
C(OH)2:C(OH).C02H.  That  this  view  is  correct  has  been 
shown  by  the  artificial  preparation  of  uric  acid. 

It  will  be  seen  that  uric  acid  contains  residues  not  only  of 
urea,  but  of  parabanic  acid,  of  barbituric  acid,  and  of  a  ureid 
of  mesoxalic  acid  (alloxan). 

Uric  acid  and  related  compounds  are  regarded  as  derived 
from  a  compound  of  the  formula 

(1)    N  =  CH(6) 

I  I     (?) 
(2)HC  (5)C-NH 

II  II 
(3)    N  -  C- 

(4)<  (9) 

to  which  the  name  purine  has  been  given. 

A  careful  study  of  uric  acid  has  shown  that  it  is  a  tauto- 
meric  compound.  It  may  be  represented  by  either  one  of  the 
two  formulas, 

NH-CO  N-C.OH 

II  II 

CO       C-NH\  or         HO.C      C-NHv 

I          II  >CO  II      ||  J>C.OH. 

NH-C-NH'  N-C-N^ 

According  to  the  latter  formula  it  is  a  2,  6,  8-trihydroxypurine. 


Xanthine,  2,  6-dihydroxypurine,  CgH^Oa,  is  found  in 
all  the  tissues  of  the  body  and  in  the  urine,  in  some  rare 
urinary  calculi,  and  in  several  animal  liquids.  It  is  formed 
by  the  action  of  nitrous  acid  on  guanine :  — 

C5H5N50  +  HN02  =  C5H4N402  +  H20  +  N2. 

In  this  case  the  nitrous  acid  causes  a  substitution  of  an 
hydroxyl  group  for  an  ammo  group. 


226        MIXED    COMPOUNDS   CONTAINING   NITROGEN 


,  [C5H2(CH3)2N4OJ,  is    , 

substance  found  in  chocolate  prepared  from  the  seed  of  the 
cacao  tree.  It  has  been  made  by  treating  the  lead  compound 
of  xanthine  with  methyl  iodide. 

Caffeine,  theine,  trimethyl-xanthine, 

C8H10N4O2  +  H2O[C5H(CH3)3N4O2  +  H2O],  is  the  active  con- 
stituent of  coffee  and  tea.  It  has  been  made  from  theo- 
bromine  by  the  introduction  of  a  third  methyl  group. 

Thus,  as  will  be  seen,  a  close  connection  is  established  be- 
tween the  active  constituents  of  coffee,  tea,  and  chocolate  on 
the  one  hand,  and  xanthine  and  guanine  on  the  other. 

Guanine,  2-amino,  6-hydroxypurine. 

OaHfiNgOCGsHsCNHaJ^Q],  is  found  principally  in  guano, 
from  which  it  is  prepared.  Nitrous  acid  converts  it  into 
xanthine.  Oxidizing  agents  convert  it  into  guanidine,  CN3Hj 
(see  p.  217). 

Polypeptides.  —  These  are  compounds  which  have  been 
prepared  from  amino-acids  and  acid  amides.  The  simplest 
example  is  glycyl-glytine,  a  compound  of  glycine  of  the  con- 
stitution NH2.CH2.CO.NH.CH2.C02H.  As  will  be  seen, 
it  contains  the  glycyl  group,  NH2.CH2.CO,  and  this  has  taken 
the  place  of  one  of  the  hydrogen  atoms  of  the  amino  group  of 
another  molecule  of  glycine.  From  this  by  treatment,  first 
with  chloracetyl  chloride,  and  then  ammonia,  the  tripeptide, 
digly  cyl-glycine,  NH2  .  CH2  .  CONH  .  CH2.  CO  .  NH  .  CH2  .  C02H, 
is  formed.  Many  polypeptides  have  thus  been  prepared,  among 
them  being  one  containing  eighteen  carbon  atoms.  Some  poly- 
peptides have  been  obtained  by  decomposition  of  natural  albu- 
mins. Most  of  them  are  easily  soluble  in  water  and  difficultly 
soluble  in  alcohol.  The  more  complicated  polypeptides  give 
the  biuret-reaction  (see  p.  221).  All  polypeptides  can  be  hydro- 
lyzed,  yielding  the  constituent  amino  acids.  These  compounds 
are  of  special  importance  because  of  their  relations  to  the 
peptones  (which  see). 


RETROSPECT  227 

RETROSPECT 

All  the  compounds  we  have  thus  far  had  to  deal  with  may 
be  regarded  as  derived  from  the  marsh-gas  hydrocarbons  or 
paraffins.  These  are,  (1)  the  substitution-products  of  the  hydro- 
carbons; (2)  alcohols ,  of  which  there  are  three  classes:  (a)  the 
primary,  (6)  the  secondary,  and  (c)  the  tertiary  alcohols;  (3) 
aldehydes;  (4)  Tcetones;  (5)  acids. 

Acids  and  alcohols  act  upon  each  other,  forming  (6)  ethereal 
salts,  and  alcohols  can  be  converted  into  (7)  ethers. 

Corresponding  to  the  oxygen  derivatives,  there  are  com- 
pounds containing  sulphur,  as  (8)  the  sulphur  alcohols  or  mer- 
captans;  (9)  the  sulphur  ethers ;  and  (10)  the  sulphonic  acids. 

Under  the  head  of  compounds  containing  nitrogen  occur 
cyanogen  and  the  allied  compounds  hydrocyanic,  cyanic,  and 
sulpho-cyanic  acids.  Related  to  these  are  (11)  the  cyanides, 
and  (12)  the  isocyanides;  (13)  the  cyanates,  and  (14)  the  iso- 
cyanates;  (15)  the  sulpho-cyanates,  and  (16)  the  iso-sulpho- 
cyanates  or  mustard-oils. 

Finally,  there  are  (17)  compounds  containing  metals  in  com- 
bination  with  radicals. 

Then  there  are  poly-acid  alcohols  and  poly-basic  acids. 

Under  the  head  of  mixed  compounds  were  found  compounds 
which  belong  at  the  same  time  to  two  or  more  of  the  funda- 
mental classes,  as  the  hydroxy-acids,  the  carbo-hydrates,  and  the 
amino-acids.  A  study  of  the  amino-acids  and  the  acid  amides 
led  naturally  to  urea  and  its  derivatives,  to  uric  acid  and  its 
derivatives,  and  to  the  polypeptides. 

We  turn  now  to  a  new  class  of  compounds,  known  as  unsatu- 
rated  compounds. 


CHAPTER   XIII 

UNSATURATED  CARBON  COMPOUNDS  —  DISTINCTION  BE- 
TWEEN SATURATED  AND  UNSATURATED  COMPOUNDS 

MOST  of  the  compounds  thus  far  studied  are  generally  called 
saturated  compounds.  This  is  an  appropriate  name  so  far  as 
the  hydrocarbons  themselves  and  some  of  the  classes  of  their 
derivatives  are  concerned.  The  expression  "saturated"  is  in- 
tended to  signify  that  the  compounds  have  no  power  to  unite 
directly  with  other  compounds  or  elements.  Thus,  marsh  gas 
cannot  be  made  to  unite  directly  with  anything.  Bromine,  for 
example,  must  first  displace  hydrogen  before  it  can  enter  into 
combination  :  —  _  HBr 


The  compound  is  saturated. 

On  the  other  hand,  a  compound  that  can  take  up  elements 
or  other  compounds  directly  is  called  unsaturated.  Thus, 
phosphorus  trichloride  is  unsaturated,  for  it  has  the  power 
to  take  up  two  chlorine  ,  atoms,  thus  :  — 


Ammonia  is  unsaturated,  for  it  can  take  up  an  equivalent  of 
an  acid  :  - 


The  condition  of  unsaturation  is  met  with  among  carbon 
compounds  in  several  forms  :  — 

First.  The  aldehydes  act  like  unsaturated  compounds,  as 
shown  in  their  power  to  take  up  ammonia,  hydrocyanic  acid, 
and  other  substances. 

Second.  The  ketones  also  act  like  unsaturated  compounds, 
though  their  power  in  this  way  is  less  marked  than  that  of  the 
aldehydes. 

Third.  The  substituted  ammonias  are  unsaturated,  in  the 
same  sense  that  ammonia  itself  is  unsaturated. 

228 


UNSATURATED  CARBON  COMPOUNDS       229 

Fourth.  The  cyanides  take  up  hydrogen  directly,  and  are 
therefore  unsaturated  also. 

In  the  substituted  ammonias  the  unsaturation  is  due  to  the 
same  cause  as  that  in  ammonia.  In  them  the  nitrogen  is  tri- 
valent.  In  contact  with  acids  it  becomes  quinquivalent,  and 
saturates  itself. 

In  the  cyanides  carbon  and  nitrogen  are  probably  linked 
together  in  a  different  way  from  that  in  the  substituted 
ammonias,  and  when  hydrogen  is  added  to  the  cyanogen 
group,  —  C  1  N,  the  condition  is  changed  to  that  which  is 
characteristic  of  the  substituted  ammonias:  — 


In  the  aldehydes  and  ketones,  carbon  is  in  combination  with 
oxygen  in  the  carbonyl  condition.  When  they  unite  with 
hydrogen  and  some  compounds,  such  as  hydrocyanic  acid,  the 
relation  between  the  carbon  and  oxygen  is  probably  changed 
to  the  hydroxyl  condition.  The  changes  are  usually  repre- 
sented by  formulas  such  as  the  following:  — 


(CH3)2C  =  0  +  HCN  = 

In  carbonyl  the  oxygen  is  represented  as  held  by  two  bonds 
to  the  carbon  atom,  while  in  hydroxyl  it  is  represented  as  held 
by  one  bond.  The  signs  may  be  used  if  not  too  literally  inter- 
preted. There  are  undoubtedly  two  relations  which  carbon 
and  oxygen  bear  to  each  other  in  carbon  compounds.  These 
relations  may  be  called  the  hydroxyl  relation,  represented  by 
the  sign  C  —  0  —  ,  and  the  carbonyl  relation,  represented  by  the 
sign  C  =  0. 

Fifth.  There  is  a  fifth  kind  of  unsaturation,  dependent  upon 
differences  in  the  relations  between  carbon  atoms,  and  it  is  this 
kind  which  is  ordinarily  meant  when  unsaturated  carbon  com> 
pounds  are  spoken  of. 


230       UNSATURATED  CARBON  COMPOUNDS 

The  kind  of  relation  between  the  carbon  atoms  in  all  the 
saturated  hydrocarbons  is,  so  far  as  we  know,  the  same  as  that 
which  exists  between  the  two  carbon  atoms  of  ethane,  and 
this  is  represented  by  the  formula  H3C  —  CH3.  This  formula 
signifies  simply  that  the  two  carbon  atoms  are  held  together 
by  the  forces  which  in  marsh  gas  enabled  each  methyl  group  to 
hold  one  hydrogen  atom.  Abstracting  one  hydrogen  atom  from 
marsh  gas,  union  is  effected  between  the  carbon  atoms.  What 
would  result  if  two  hydrogen  atoms  were  to  be  abstracted,  and 
union  between  the  carbons  then  effected  ?  Theoretically  we 
should  get  a  compound  made  up  of  two  groups  CH2,  thus 
CH2.CH2,  and  presumably  the  relation  between  the  carbon 
atoms  in  this  compound  would  be  different  from  the  relation 
between  the  carbon  atoms  in  ethane.  Without  pushing  these 
speculations  farther,  it  may  be  said  that  there  is  a  well-known 
hydrocarbon  of  the  formula  C2H4  which  differs  markedly  from 
ethane.  It  shows  the  property  of  unsaturation  very  clearly. 
This  is  olefiant  gas  or  ethylene.  It  is  the  first  of  an  homologous 
series  of  hydrocarbons,  only  a  few  of  which  are  well  known. 
These  hydrocarbons  yield  derivatives  like  the  paraffins ; 
though  of  these,  as  well  as  of  the  hydrocarbons,  very  few 
are  known  as  compared  with  the  number  of  the  paraffin 
derivatives. 

ETHYLENE  AND  ITS  DERIVATIVES 
HYDROCARBONS,  C^H.^  THE  OLEFINES 

The  principal  hydrocarbons  of  this  series  are  included  in 
the  subjoined  table :  — 

Ethylene,     Ethene C2H4. 

Propylene,   Propene C3H6. 

Butylene,     Butene C4H8. 

Amylene,      Pentene C5Hi0. 

Hexylene,     Hexene C6H12. 

Heptylene,  Heptene C7H14. 


UNSATURATED  CARBON  COMPOUNDS       231 

The  members  are  homologous  with  ethylene.  They  bear  to 
the  paraffins  a  very  simple  relation,  each  one  containing  two 
atoms  of  hydrogen  less  than  the  paraffin  with  the  same  number 
of  carbon  atoms. 

Ethylene,  olefiant  gas,  C2H4(CH2  =  CH2).  —  This  gas  is 
formed  when  many  organic  substances  are  subjected  to  dry 
distillation.  The  two  principal  reactions  which  yield  it  are  :  — 

(1)  The  action  of  an  alcoholic  solution  of  potassium  hydrox- 
ide on  ethyl  chloride,  bromide,  or  iodide  :  — 

C2H5Br  +  KOH  =  C2H4  -f  KBr  +  H20. 

This  is  the  most  important  reaction  for  the  preparation  of  the 
unsaturated  compounds  of  the  ethylene  series.  It  is  applicable 
not  only  to  the  hydrocarbons  but  to  substances  belonging  to 
other  classes.  By  means  of  it  it  is  possible  to  pass  from 
any  saturated  compound  to  the  corresponding  unsaturated  com- 
pound of  the  ethylene  series.  Thus  we  can  pass  from  ethane, 
C2H6,  to  ethylene,  C2H4,  by  first  introducing  bromine,  and  then 
abstracting  hydrobromic  acid  from  the  mono-bromine  substi. 
tution-product.  By  treating  the  mono-bromine  substitution 
products  of  other  saturated  compounds  in  the  same  way,  the 
corresponding  unsaturated  compounds  can  be  made. 

(2)  The  action  of  sulphuric  acid  and  other  dehydrating  agents 
upon  alcohol  :  — 


Experiment  50.  In  a  I1  flask  put  a  mixture  of  100ec  alcohol  and  200CC 
ordinary  concentrated  sulphuric  acid  and  add  25e  dehydrated  alum  and  a 
little  paraffin.  Heat  to  157°  to  175°.  Pass  the  gas  through  three  wash 
bottles  containing,  in  order,  sulphuric  acid,  caustic  soda,  and  sulphuric 
acid.  Then  pass  it  into  bromine  contained  in  a  cylinder,  provided  with 
a  cork  with  two  holes.  If  the  cylinder  has  a  diameter  of  about  5cm,  let 
the  layer  of  bromine  be  about  5cm  to  7cm  deep.  Upon  it  pour  a  somewhat 
deeper  layer  of  water.  Place  the  cylinder  in  a  vessel  containing  cold 
water.  Pass  the  gas  into  the  bromine  until  it  is  completely  decolorized 
(See  note,  next  page.) 


232        UNSATURATED  CARBON  COMPOUNDS 

Ethylene  is  a  colorless  gas  which  can  be  condensed  to  a 
liquid;  It  burns  with  a  luminous  flame.  With  oxygen  it 
forms  a  mixture  which  explodes  when  ignited.  Its  most  char" 
acteristic  property  is  its  power  to  unite  directly  with  other  sub- 
stances, particularly  with  the  halogens  and  with  the  hydrogen  acids 
of  the  halogens.  Thus  it  unites  with  chlorine  and  bromine,  and 
with  hydriodic  and  hydrobromic  acids :  — 

C2H4  +  C12  =  C2H4C12; 
C2H4  +  Br2  =  C2H4Br25 
C2H4  +  HBr  =  C2H5Br; 
C2H4  4-  HI  =  C2H5I. 

The  products  formed  with  chlorine  and  bromine  are  called 
ethylene  chloride  and  ethylene  bromide.  They  have  been  men- 
tioned under  the  head  of  halogen  derivatives  of  the  paraffins. 
They  are  isomeric  with  ethylidene  chloride  and  etliylidene  bromide, 
which  are  formed  by  direct  substitution  of  chlorine  or  bromine 
for  two  hydrogens  of  ethane. 

NOTE. — The  addition  of  bromine  to  ethylene  is  illustrated  by  the 
experiment  last  performed,  in  which  ethylene  bromide  is  formed.  To 
purify  the  product,  put  a  little  dilute  caustic  soda  in  the  cylinder,  and  shake. 
Remove  the  upper  layer  of  water,  and  repeat  the  washing  with  dilute 
caustic  soda.  Then  wash  with  water  two  or  three  times,  each  time  remov- 
ing the  water  with  the  aid  of  a  separating  funnel.  Finally,  put  the  oil  in  a 
flask,  add  a  few  pieces  of  granulated  calcium  chloride,  and  allow  to  stand. 
Pour  off  into  a  dry  distilling-bulb,  and  distil,  noting  the  temperature. 

A  question  that  may  fairly  be  asked  concerning  the  structure 
of  ethylene  is  this :  Does  it  consist  of  two  groups,  CH2,  or  of 
a  methyl  group,  CH3,  and  CH?  Is  it  to  be  represented  by  the 
formula  CH2.CH2  or  CH3.CH?  Perhaps  the  clearest  answer 
to  this  question  is  found  in  the  fact  that  the  chloride  formed 
by  addition  of  chlorine  to  ethylene,  and  that  formed  by  replac- 
ing the  oxygen  in  aldehyde  by  chlorine,  are  not  identical.  All 
evidence  is  in  favor  of  the  view  that  aldehyde  is  correctly 

represented  by  the  formula  CH3.C^fH.     Hence,  as  has  been 


ALCOHOLS  233 

pointed  out,  the  chloride  obtained  from  it  must  be  represented 
thus,  CH3.CHC12.  Hence,  further,  it  appears  highly  probable 
that  the  isoineric  chloride  obtained  from  ethylene  must  be 
represented  thus,  CH2C1.CH2C1.  Now,  as  this  substance  is 
formed  by  direct  addition  of  chlorine  to  ethylene,  ethylene  has 

CH2  CH3 

the  formula  I      ,  and  not  I 

CH2  CH 

Nothing  is  known  in  regard  to  the  relation  between  the  two 
carbon  atoms  of  ethylene,  except  that  it  is  probably  different 
from  that  which  exists  between  the  carbon  atoms  of  ethane. 
It  is  usually  represented  by  the  sign  (=),  or  two  dots  (:); 

CH2 
thus,  II     or  CH2:CH2.     The  question  as  to  the  relation  between 

CH2 

the  carbon  atoms  in  ethylene  must  be  left  open.  If  either  of 
the  above  signs  is  used,  it  should  serve  mainly  as  an  indication 
of  the  kind  of  unsaturation  in  ethylene,  the  compound  in  whose 
formula  it  is  written  having  the  power  to  take  up  two  atoms  of 
bromine,  a  molecule  of  hydrobromic  acid,  etc. 

The  homologues  of  ethylene  bear  the  same  relation  to  it  that 
the  homologues  of  ethane  bear  to  this  hydrocarbon.  Propylene 

CH.CH3 
is  methyl-ethylene,  II  ,  just  as  propane  is  methyl-ethane, 

CH2.CH3  CHs  CH.CH3         C(CH3)2, 

I  .     Butylene  is  dimethyl-ethylene,  II  ,  or  II 

CH3  CH.C2H5  CH.CH3         CH2 

or  ethyl-ethylene,   II  .     That  is   to   say,   in  the  hydro- 

CH2 

carbons  of  the  ethylene  series  the  ethylene  condition  between 
carbon  atoms  occurs  only  once. 

ALCOHOLS,  CnH2nO 

These  alcohols  bear  to  the  ethylene  hydrocarbons  the  same 
relation  that  the  alcohols  of  the  methyl  alcohol  series  bear  to 
the  paraffins.  Only  one  is  well  known.  This  is  the  second 
member,  corresponding  to  propylene. 


234        UNSATURATED  CARBON  COMPOUNDS 

Allyl  alcohol,  C3H6O(CH2:CH.CH2OH).  — This  alcohol 
is  formed  in  several  ways  from  glycerol. 

1.  By  introducing  two  chlorine  atoms  into  glycerol  in  the 
place  of  two  hydroxyls,  thus  getting  dichlorhydrin,  C3H5C12.OH : 

CH2OH  CH2C1 

TTP1 

CHOH  +  Trni  =  CHC1     +  2  H20 ; 
I  I 

CH2OH  CH2OH 

and  treating  the  dichlorhydrin  with  sodium,  which  extracts  the 
chlorine :  — 

CH2C1  CH2 

I  II 

CHC1     +  2  Na  =  CH        +  2  NaCl. 

I-  I 

CH2OH  CH2OH 

2.  By  treating  glycerol  with  the  iodide  of  phosphorus.     This 
gives  allyl  iodide,  C3H5I.      By  treating  the  iodide  with  silver 
hydroxide  it  is  converted  into  the  alcohol. 

3.  Most  readily  by  heating  glycerol  with  oxalic  acid,  as  in 
the  preparation  of  formic  acid.     The  mixture  is  heated  to  260°, 
when  allyl  alcohol  passes  over.     The  first  product  formed  in 
this  case  is   an  ethereal    salt  of  formic  acid  with  glycerol, 
HOH2C.CHOH.CH2O.COH.     At  a  higher  temperature  this 
breaks  down,  yielding  allyl  alcohol,  HOH2C.CH :  CH2,  carbon 
dioxide  and  water. 

Allyl  alcohol  is  a  colorless  liquid  boiling  at  96.5°.  It  has  a 
disagreeable  penetrating  odor  and  is  miscible  with  water  in  all 
proportions. 

Nascent  hydrogen  does  not  act  upon  it,  or  at  least  the  action, 
if  any,  takes  place  with  difficulty.  As  far  as  composition  is 
concerned,  the  relation  between  allyl  alcohol  and  propyl  alco- 
hol is  the  same  as  that  between  ethylene  and  ethane :  — 


ALLYL   MUSTAKD-OIL  235 

Allyl  alcohol  forms  esters  with  acids  and  gives  the  other  re- 
actions for  alcoholic  hydroxyl.  It  is,  further,  a  primary 
alcohol,  as  it  is  converted  by  certain  oxidizing  agents  into  the 
corresponding  aldehyde  (acrolei'n)  and  acid  (acrylic  acid). 

When  treated  with  a  dilute  solution  of  potassium  permanga- 
nate it  is  converted  into  glycerol  :  — 

CH2  CH2OH 

II  I 

CH        +0  +  H20=CHOH. 
I  I 

CH2OH  CH2OH 

Allyl  compounds  --  Among  the  derivatives  of  allyl  alcohol 
which  are  of  special  interest  is  allyl  sulphide  (C3H5)2S,  which 
is  the  chief  constituent  of  the  oil  of  garlic.  It  can  be  made 
artificially  by  treating  allyl  iodide  with  potassium  sulphide  :  —  • 

2  C3H5I  +  K2S  =  (C3H5)2  S  +  2  KL 

It  is  a  colorless,  oily  liquid  of  a  disagreeable  odor,  only  slightly 
soluble  in  water. 

Allyl  mustard-oil,  SON  .  C3H5.  —  Under  Sulpho-cyanates 
mention  was  made  of  a  series  of  isomeric  compounds  called 
isosulpho-cyanates  or  mustard-oils.  The  sulpho-cyanates 
of  the  alcohol  radicals  are  made  from  potassium  sulpho- 
cyanate.  Thus,  methyl  sulpho-cyanate  is  made  by  mixing 
together  potassium  methyl-sulphate  and  potassium  sulpho- 
cyanate,  and  distilling:  — 

riTT  r\ 

NCSK  +  >  s°2  =  K2S04  +  NCSCH3. 


The  mustard-oils,  on  the  other  hand,  are  made  by  a  com- 
plicated reaction  from  carbon  bisulphide  and  substituted 
ammonias.  The  conduct  of  the  sulpho-cyanates  led  to  the 
conclusion  that  they  must  be  represented  by  the  formula 
NO  —  SR,  while  that  of  the  isosulpho-cyanates  or  mustard-oils 


236      UNSATUKATED  CARBON  COMPOUNDS 

led  to  the  formula  SC  —  NR,  as  representing  their  structure. 
Allyl  mustard-oil  is  the  chief  representative  of  the  class  of 
bodies  known  as  mustard-oils.  It  occurs  as  a  glucoside  (which 
see)  in  mustard  seed.  From  the  glucoside  it  is  formed  by 
the  action  of  an  enzyme.  It  also  occurs  in  horse-radish.  It  is 
formed  by  treating  allyl  iodide  with  potassium  sulpho-cyanate. 
If  this  reaction  consisted  simply  in  the  substitution  of  the  ally] 
group,  C3H5,  for  potassium  the  product  should  be  allyl  sulpho- 
cyanate,  C3H5S  —  CN.  As  a  matter  of  fact  it  is  the  isosulpho- 
cyanate  C3H5lSr  — CS.  As  has  already  been  pointed  out  (see 
p.  94),  the  sulpho-cyanates  are  converted  into  the  isosulpho- 
cyanates  by  heat,  so  that  the  formation  of  the  isosulpho- 
cyanate  in  this  case  is  not  surprising. 

Allyl  mustard-oil  is  a  liquid,  boiling  at  150.7°,  and  having  a 
very  pungent  odor. 

Zinc  and  hydrochloric  acid  convert  it  into  allyl-amine, 
NH2.C3H5,  and  thioformic  aldehyde,  H2CS.  This  reaction 
indicates  that  in  allyl  mustard-oil  the  radical  allyl  is  in  com- 
bination with  the  nitrogen  and  not  with  the  sulphur. 

NOTE  FOR  STUDENT.  —  "What  change  do  the  mustard-oils  in  general 
undergo  when  treated  with  nascent  hydrogen  ?  What  change  do  the 
sulpho-cyanates  undergo  when  oxidized? 

Acrolein,  acrylic   aldehyde,  C3H4O(CH2:  CH.  COH). — 

Acrolei'n  can  be  made  by  careful  oxidation  of  allyl  alcohol.  It 
is  formed  by  the  dry  distillation  of  impure  glycerol,  which 
breaks  up  into  water  and  acrolein :  — 

C3H803=C3H40+2H20. 

It  is,  hence,  formed  also  by  heating  the  ordinary  fats,  the 
peculiar  penetrating  odor  noticed  when  fatty  substances  are 
heated  to  a  sufficiently  high  temperature  being  due  to  the 
formation  of  acrolein.  It  is  prepared  best  by  heating  glycerol 
with  boric  acid. 


CROTONIC    ALDEHYDE  237 

Experiment  51.  In  a  test-tube  mix  anhydrous  glycerol  (1  part) 
and  boric  acid  (2  parts),  and  heat  the  mixture.  Pass  the  vapors  through 
a  bent  tube  into  water  contained  in  another  test-tube.  Notice  the  odor. 
Try  the  effect  on  a  dilute  solution  of  nitrate  of  silver.  What  is  the  mean- 
ing of  this  reaction  ? 

Acrole'in  is  a  volatile  liquid  which  boils  at  52.4°.  It  has  an 
extremely  penetrating  odor,  and  its  vapor  acts  violently  upon 
the  eyes,  causing  the  secretion  of  tears. 

Acrole'in  takes  up  oxygen  from  the  air,  and  is  converted  into 
the  corresponding  acid,  acrylic  acid,  C3H402  (which  see). 

It  takes  up  hydrogen,  and  is  thus  converted  into  allyl  alcohol. 

It  takes  up  hydrochloric  acid,  and  is  converted  into  /?-chlor- 
propionic  aldehyde:  — 

C2H3.COH  4-  HC1  =  CH2C1.CH2.COH. 

/3-Chlor-propionic  aldehyde 

The  first  two  reactions  are  characteristic  of  aldehydes  in 
general ;  the  last  one  is  characteristic  of  unsaturated  compounds 
belonging  to  the  ethylene  group.  Acrole'in,  like  ordinary  alde- 
hyde, forms  polymeric  modifications  which  can  easily  be 
reconverted  into  acrolein. 

It  unites  with  ammonia,  forming  acrolein-ainmonia,  and  with 
other  substances  in  much  the  same  way  as  ordinary  aldehyde 
does.  It  unites  with  bromine  to  form  acrolein  dibromide,  which 
when  treated  with  barium  hydroxide  gives  i-fructose  (which  see). 

Crotonic  aldehyde,  C4H6O(CH3.CH  :  CH.  COH).  —  This 

aldehyde  is  most  readily  made  by  distilling  aldol  (which  see). 
The  starting-point  is  acetic  aldehyde.  By  treatment  with 
potassium  carbonate  in  aqueous  solution  the  acetic  aldehyde  is 
condensed  (aldol  condensation)  to  aldol  or  /3-hydroxy-butyric 
aldehyde,  CH3.CH(OH).CH2.COH.  By  distillation  this  breaks 
down  into  crotonic  aldehyde  and  water :  — 

CH3.CH(OH).CH2.COH  =  CH3.CH:CH.COH  +  H20. 


238  UNSATURATED   CARBON   COMPOUNDS 

ACIDS,  CnHjjn.aOa 

Running  parallel  to  the  ethylene  series  of  hydrocarbons,  and 
bearing  the  same  relation  to  it  that  the  fatty  acid  series  bears 
to  the  paraffins,  is  a  series  of  acids  of  which  the  first  member 
is  acrylic  acid,  C3H402.  Several  members  of  the  series  are 
known.  The  principal  members  are  named  in  the  subjoined 
table:  — 

ACRYLIC  ACID  SERIES 

ACIDS,  C^H^^Og 

Acrylic          acid CgH^Oa. 

Crotonic  " C^O* 

Angelic  « C5H802. 

Hydrosorbic     « C6H1(A, 

Teracrylic  «  C7HuOa. 

Cimic  " CtfHaA. 

Hypogaeic  " C^HgoO-j. 

Oleic  « CisH^O* 

Erucic  " 


Of  most  of  the  higher  members  of  the  series  several  isomeric 
modifications  are  known.  Only  a  few  of  these  acids  will  be 
treated  of  here. 

Acrylic  acid,  C3H4O2(CH2:  CH.CO2H).  — This  acid  has 
already  been  mentioned  in  connection  with  hydracrylic  acid, 
which,  when  heated,  breaks  up  into  acrylic  acid  and  water :  — 

CH2OH .  CH2. C02H  =  CH2 :  CH .  C02H  +  H20. 

Hydracrylic  acid  Acrylic  acid 

NOTE  FOR  STUDENT.  —  This  reaction  is  analogous  to  that  which  takes 
place  when  ordinary  alcohol  is  converted  into  ethylene.  In  what  does  the 
analogy  consist  ?  What  acid  is  isomeric  with  hydracrylic  acid  ?  How 
does  it  conduct  itself  when  heated  ?  Compare  the  transformation  of 
hydracrylic  acid  into  acrylic  acid  with  that  of  malic  into  maleic  and 
fumaric  acids,  and  with  that  of  citric  into  aconitic  acid. 


CROTONIC   ACIDS  239 

Acrylic  acid  can  be  made  by  careful  oxidation  of  acrolein 
with  silver  oxide.  The  relations  between  propylene,  C3H6, 
allyl  alcohol,  C3H5.OH,  acrolein,  C2H3.COH,  and  acrylic  acid, 
C2H3.CO2H,  are  the  same  as  those  between  any  hydrocarbon 
of  the  paraffin  series,  and  the  corresponding  primary  alcohol, 
aldehyde,  and  acid. 

Acrylic  acid  can  be  made  further  by  treating  /?-iodo-propionic 
acid  with  alcoholic  caustic  potash :  — 

CH2I.CH2.C02H  =  CH2:CH.C02H  +  HI. 

NOTE  FOR  STUDENT.  —  Compare  this  reaction  with  that  by  which 
ethylene  is  made  from  ethyl  bromide. 

Acrylic  aci<f  is  a  liquid  having  a  pungent  odor.  It  boils  at 
140°,  and  melts  at  13°. 

Nascent  hydrogen  converts  it  into  propionic  acid.  Hydriodic 
acid  unites  directly  with  it,  forming  /?-iodo-propionic  acid. 

NOTE  FOR  STUDENT.  —  What  are  the  analogous  reactions  with  allyl 
alcohol  and  acrolein  ? 

Crotonic  acids,  C4H6O2. — Two  crotonic  acids,  the  ordi- 
nary solid  form  and  isocrotonic  acid,  occur  in  croton  oil  and 
in  crude  pyroligneous  acid.  Ordinary  or  solid  crotonic  acid 
is  formed,  (1)  by  hydrolyzing  allyl  cyanide;  (2)  by  distilling 
/2-hydroxy-butyric  acid;  (3)  by  treating  a-brom-butyric  acid 
with  alcoholic  caustic  potash;  (4)  by  heating  malonic  acid 
with  paraldehyde  and  acetic  anhydride. 

Allyl  cyanide  has  been  shown  to  have  the  structure 
CH3.CH:CH.C]Sr,  although  it  is  formed  from  allyl  bromide, 
which  must  have  the  structure  CH2 :  CH .  CH2Br,  because  this 
is  formed  by  the  action  of  hydrobromic  acid  on  allyl  alcohol. 
It  follows  that  the  structure  of  crotonic  acid  should  be  repre- 
sented by  the  formula  CH3.CH  :  CH.  C02H.  The  formation  of 
crotonic  acid  from  a-brom-butyric  acid,  CH3.CH2.CHBr.C02H, 
by  the  abstraction  of  hydrobromic  acid  leads  to  the  same 


240       UNSATURATED  CARBON  COMPOUNDS 

conclusion.      So   also   the   formation  of    crotonic    acid    from 
paraldehyde  and  malonic  acid  points  to  the  formula 

CH3.  CH  :  CH  .  C02H  for  crotonic  acid  :  — 


(1)  CH3. 

Aldehyde  Malonic  acid 

O  TT 

2 


(2)  CH3.CH: 

Crotonic  acid 


Again,  when  crotonic  acid  is  fused  with  caustic  potash,  it  gives 
only  acetic  acid  :  — 

C4H602  +  H20  +  0  =F  2  C2H402  ;  % 

and,  as  it  has  been  shown  that  under  these  circumstances  the 
breaking  down  takes  place  at  the  place  where  the  double  bond 
occurs,  this  reaction  furnishes  additional  evidence  in  favor  of 
the  view  that  ordinary  crotonic  acid  has  the  constitution 
represented  by  the  formula  CH3.CH  :  CH.C02H. 

Isocrotonic  acid  contains  the  same  groups  as  crotonic  acid, 
and  is  also  to  be  represented  by  the  formula 

CH3.CH:CH.C02H. 

As  will  be  shown  under  maleic  and  fumaric  acids  (which  see), 
the  difference  between  the  two  forms  of  crotonic  acid  is  proba- 
bly due  to  the  difference  in  the  arrangement  of  the  groups  in 
space. 


Ole'ic  acid,  (VE^O^  —  This  acid  was  referred  to  in  con- 
nection with  the  fats,  it  being  one  of  the  three  acids  found 
most  frequently  in  combination  with  glycerol.  Olein,  or 
glyceryl  tri-oleate,  is  the  liquid  fat,  and  is  the  chief  con- 
stituent of  the  fatty  oils,  such  as  olive  oil,  whale  oil,  etc.,  and 
of  the  fats  of  cold-blooded  animals.  It  is  contained  also  in 
almost  all  ordinary  fats.  In  the  preparation  of  stearic  acid 
for  the  manufacture  of  candles,  the  olei'c  acid  is  pressed  out 


POLYBASIC    ACIDS    OP    THE   ETHYLENE    GROUP       241 

of  the  mixture  of  fatty  acids.  To  prepare  the  acid,  olei'n  is 
saponified,  and  the  soap  then  decomposed  with  hydrochloric 
acid. 

Olei'c  acid  is  a  colorless  oil  that  solidifies  when  cooled,  form- 
ing crystals  that  melt  at  14°.  It  unites  with  bromine,  forming 
dibromstearic  acid.  Hydriodic  acid  converts  it  into  stearic 
acid  :  — 

Ci8H3402  +  H2  =  C18H3602. 

Oleic  acid  Stearic  acid 

This  same  change  can  be  effected  in  other  ways  and  the  reac- 
tion is  utilized  on  the  large  scale. 

POLYBASIC  ACIDS  OF  THE  ETHYLENE  GROUP 

There  are  a  few  dibasic  acids  that  bear  to  the  ethylene 
hydrocarbons  the  same  relations  that  the  members  of  the 
oxalic  acid  series  bear  to  the  paraffins.  They  may  be  regarded 
as  derived  from  the  hydrocarbons  by  the  introduction  of  two 
carboxyl  groups. 

Acids,  C2H2(CO2H)2.  —  There  are  two  acids  of  this  formula, 
fumaric  and  maleic  adds,  both  of  which  are  formed  by  the 
distillation  of  malic  acid.  Fuinaric  acid  remains  in  the  retort  ; 
maleic  anhydride  distils  over. 

Fumaric  acid  can  also  be  made  by  treating  brom-succinic 
acid  with  alcoholic  potash. 

Both  fumaric  and  maleic  acids  are  converted  into  succinic 
acid  by  nascent  hydrogen,  and  into  the  same  brom-succinic 
acid  by  hydrobromic  acid.  Both  combine  with  water  to  form 
the  same  malic  acid.  They  are,  therefore,  structurally  the 
same,  and  both  must  be  represented  as  ethylene-dicarboxylic 

CH.C02H 

acids    II  .     They  are  hence  stereo-isomeric  :  — 

CH.C02H 


Malic  acid  Maleic  or  Fumaric  acid 


242 


UNSATURATED  CARBON  COMPOUNDS 


C2H3Br  <       *          =  C2H2  <       2     +  HBr 


Brom-succinic  acid 

C02H 


Fumaric  acid 


C0H 


Maleic  or  Fumaric  acid 


Succinic  acid 


An  extension  of  the  fundamental  ideas  of  stereochemistry 
furnishes  a  plausible  explanation  of  the  relation  between  maleic 
and  fumaric  acids.  According  to  these  ideas,  a  carbon  atom  in 
combination  with  four  atoms  or  groups  of  atoms  holds  these 
atoms  or  groups  by  bonds  directed  toward  the  solid 
angles  of  a  tetrahedron,  the  carbon  atom  itself 
being  at  the  centre  of  the  tetrahedron.  When  two 
carbon  atoms  unite  in  the  simplest  way,  the  stereo- 
chemical  model  representing  the  compound  consists 
of  two  tetrahedrons  united  at  one  of  the  solid  angles 
of  each,  thus  :  — 


When  two  carbon  atoms  unite  by  a  double  bond, 
as  in  the  ethylene  compounds,  the  model  consists 
of  two  tetrahedrons  united  by  one  of  the  edges  of 
each,  thus :  — 


In  case  each  carbon  is  in  combination  with  two  unlike  atoms 
or  groups,  there  are  two  ways  in  which  these  can  be  arranged 
in  space,  as  shown  by  the  figures :  — 


POLYBASIC   ACIDS    OF   THE  ETHYLENE   GROUP       243 


It  will  be  seen  that,  in  the  first  of  these  figures,  the  A' a  are 
on  one  side,  and  the  B's  on  the  other  side ;  while  in  the  second 
figure  A  and  B  are  on  one  side  and  B  and  A  on  the  other. 
The  two  arrangements  are  different.  In  malei'c  and  fumaric 
acids  each  carbon  atom  is  in  combination  with  one  hydrogen 
atom  and  one  carboxyl  group,  as  shown  in  the  ordinary 

CH .  CO2H 
formula  ||  .     These  can  be  arranged  in  two  ways  cor- 

CH.C02H 
responding  to  the  above  figures,  thus :  — 


ii. 


7  COOH 


H 


COOH 


COOH     HOOC 


It  is  believed  that  figure  I.  represents  the  configuration  of 
maleic  acid,  and  figure  II.  that  of  fumaric  acid.  The  main 
reason  for  this  is  the  fact  that  when  maleic  acid  is  heated  it 
loses  water  and  forms  an  anhydride,  while  fumaric  acid  does 
not  form  an  anhydride.  As  the  anhydride  is  formed  by  the 
interaction  of  the  two  carboxyl  groups,  a  substance  of  config- 
uration I.  could  form  an  anhydride  easily  because  the  two  car- 
boxyls  are  near  enough  to  each  other  to  give  off  water,  while 
in  the  case  of  the  substance  having  the  configuration  repre- 
sented in  figure  II.  this  would  not  appear  to  be  possible. 

The  configurations  of  maleic  and  fumaric  acids  can  be  repre- 
sented by  formulas,  thus :  — 


H  -  C  -  C02H 

II 
H  -  G  -  C02H 

Maleic  acid 


H  -  C  -  CO,H 

II 
C02H  -  G  -  H 

Fumaric  acid 


244       UNSATURATED  CARBON  COMPOUNDS 

Maleic  anhydride  similarly  can  be  represented  thus :  — 

H  -  C  -  CO 

II 
H-C -CO- 

This  extension  of  the  theory  of  stereochemistry  applies  to  a 
large  number  of  phenomena  and  furnishes  a  satisfactory  ex- 
planation of  a  number  of  cases  of  isomerism  for  which  no  other 
explanation  has  been  found. 

The  two  crotonic  acids  already  referred  to  are  believed  to  be 
related  to  each  other  in  the  same  way  as  maleic  and  fumario 
acids,  as  shown  by  the  formulas :  — 

CH3-C-H  CHS-C-H 

II  II 

C02H  -C-H  H-C-  C02H 

Crotonic  acid  Isocrotonic  acid 

Acids,  C5H6O4.  —  When  citric  acid  is  rapidly  heated,  a  dis- 
tillate consisting  of  the  anhydrides  of  two  acids  of  the  formula 
CaH604  is  obtained.  These  acids  are  itaconic  and  citraconic 
acids.  When  itaconic  anhydride  is  distilled  under  ordinary 
pressure,  it  is  converted  into  citraconic  anhydride.  WThen 
citraconic  anhydride  is  heated  for  some  time  with  water  at 
150°,  itaconic  acid  is  formed.  When  a  water  solution  of  citra- 
conic  anhydride  is  treated  with  hydrochloric  or  nitric  acid  and 
then  evaporated,  a  third  acid,  memconic  acid}  isomeric  with 
citraconic  and  itaconic  acid,  is  obtained. 

It  has  been  shown  that  citraconic  and  mesaconic  acids  are 
respectively  homologues  of  maleic  and  fumaric  acids,  as  repre- 
sented by  the  formulas :  — 

CH8  -  C  -  C02H  CH3  -  C  -  C02H 

II  II 

H-C  -  C02H  C02H  -C-H 

Citraconic  acid  Mesaconic  acid 

Like  fumaric  acid,  mesaconic  acid  does  not  form  an  anhy- 


ACETYLENE  245 

dride.     Itaconic  acid  is  not  a  methyl  derivative  of  maleic  or 
fumaric  acid,  but  corresponds  to  the  formula 

CH2=C-C02H 
I 
CH2.C02H 

The  formation  of  itaconic  and  citraconic  anhydrides  from 
aconitic  acid  is  shown  thus :  — 

CH.C02H  CH2  CH.C 


C.C02H  G.CO     v 

I  'I  /O  or    | 

CH2 .  C02H  CH2 .  CO'  CHa 

Aconitic  acid  Itaconic  anhydride  Citraconic  anhydride 


C.CO^ 

,r\ 

,/ 


Aconitic  acid,  C6H6O6[C8H3(CO2H)3].  —  Aconitic  acid  is 
the  only  tri-basic  acid  of  this  group  that  need  be  mentioned. 
As  has  been  stated,  it  is  formed  when  citric  acid  is  heated  to 
175°.  It  is  found  in  nature  in  aconite  root,  and  in  the  sap  of 
sugar-cane  and  of  the  beet. 

Nascent  hydrogen  converts  it  into  tri-carballylic  acid, 
C3H5(C02H)3.  The  relation  between  citric  and  aconitic  acid 
has  already  been  pointed  out  (see  p.  182). 

ACETYLENE  AND  ITS  DERIVATIVES 

The  principal  reactions  by  means  of  which  it  is  possible  to 
pass  from  a  hydrocarbon  of  the  paraffin  series  to  the  corre- 
sponding hydrocarbon  of  the  ethylene  series  consist  in  intro- 
ducing a  halogen  into  the  paraffin,  and  then  treating  the 
mono-halogen  substitution-product  with  alcoholic  caustic 
potash  :  — 


The  effect  of  these  two  reactions  is  the  abstraction  of  two 
hydrogen  atoms  from  the  paraffin.  The  following  questions 
therefore  suggest  themselves  :  — 


246        UNSATURATED  CARBON  COMPOUNDS 

Suppose  a  dibroin  substitution-product  of  a  paraffin  should  be 
heated  with  alcoholic  caustic  potash  j  will  the  effect  be  that  rep- 
resented by  the  equation 

C2H4Br2=C2H2+2HBr? 

And,  further,  suppose  a  mono  substitution-product  of  an 
ethylene  hydrocarbon  be  treated  with  alcoholic  potash;  will 
the  effect  be  that  represented  by  the  equation 


If  so,  it  is  plain  that  we  have  it  in  our  power  to  make  a  new 
series  of  hydrocarbons,  the  members  of  which  must  bear  to  the 
ethylene  hydrocarbons  the  same  relation  that  the  latter  bear 
to  the  paraffins.  The  general  formula  of  this  series  would  be 
CnH2n_2,  that  of  the  ethylene  series  being  CnH2n,  and  that  of 
the  paraffin  series,  CnH2n+2. 

A  few  members  of  the  hydrocarbon  series,  CnH2n_2,  are 
known,  though  only  one  is  well  known,  and  this  one  alone 
need  be  taken  up  here. 

Acetylene,  ethine,  C2H2.  —  Acetylene  is  contained  in  coal 
gas  in  small  quantity.  It  is  formed  by  direct  combination 
of  hydrogen  and  carbon  when  a  current  of  hydrogen  is  passed 
between  carbon  poles  which  are  incandescent  in  consequence 
of  the  passage  of  an  electric  current;  when  alcohol,  ether, 
methane,  and  other  organic  substances  are  passed  through  a 
tube  heated  to  redness  ;  when  coal  gas  and  some  other  sub- 
stances are  burned  in  an  insufficient  supply  of  air,  as  when  a 
Bunsen  burner  "strikes  back"  ;  and  when  ethylene  bromide  is 
treated  with  alcoholic  caustic  potash  :  — 

C2H4Br2=C2H2  +  2HBr. 

It  is  formed  further  when  bromoform,  CHBr3,  or  iodolorm, 
CHI3,  is  treated  with  silver  or  zinc  dust. 

It  is  easily  made  by  the  action  of  water  on  calcium 
carbide  :  — 

C2Ca  +  2  H20  =  C2H2  +  Ca(OH)2. 


ACETYLENE 


247 


This  process  is  extensively  used  on  the  large  scale  for  the 
preparation  of  acetylene  for  illuminating  purposes. 

Experiment  52.  In  a  Woulff's  flask  or  an  ordinary  Florence  flask 
provided  with  a  dropping  funnel  and  an  outlet  tube,  put  a  few  pieces  of 
calcium  carbide  about  the  size  of  half -inch  cubes.  When  the  water  from 
the  funnel  is  allowed  to  drop  on  the  carbide  the  gas  is  given  off  at  once, 
and  the  rapidity  of  the  current  can  be  regulated  by  regulating  the  drop- 
ping of  the  water.  After  the  operation  has  been  in  progress  long  enough 
to  drive  the  air  out  of  the  apparatus,  connect  a  burner  with  the  delivery 
tube  at  A,  and  set  fire  to  the  gas.  Unless  the  burner  is  an  "  acetylene 
burner"  the  flame  gives  a  great  deal  of  soot  and  it  should  not  be  allowed 
to  burn  long.  In  the  test-tube  B  is  a  strong  solution  of  ammoniacal 
cuprous  chloride  prepared  as  follows :  Make  a  saturated  solution  of  1  part 
common  salt  and  2|  parts  crystallized  copper  sulphate.  Saturate  with 
sulphur  dioxide.  Filter,  and  wash  with  acetic  acid.  Dissolve  the  white 


Fig.  12. 

cuprous  chloride  in  ammonia.  Pass  some  of  the  gas  through  this  solu- 
tion. The  acetylene  will  be  absorbed  by  the  copper  solution,  and  a  pre- 
cipitate formed  (see  Exp.  53). 

Acetylene  is  a  colorless  gas  of  unpleasant,  leeky  odor.     It  is 
poisonous.     It  burns  with  a  luminous,  sooty  flame. 


248       UNSATURATED  CARBON  COMPOUNDS 

When  heated  to  a  sufficiently  high  temperature,  it  is  con- 
verted into  the  polymeric  substances,  benzene,  C6H6,  and  sty- 
rene,  C8H8.  It  unites  with  hydrogen  to  form  ethylene  and 
ethane.  It  unites  with  nitrogen,  under  the  influence  of  the 
sparks  from  an  induction  coil,  forming  hydrocyanic  acid:  — 


Acetylene  forms  some  curious  compounds  with  metals  and 
metallic  oxides.  Among  them  may  be  mentioned  the  copper 
compound  obtained  in  Exp.  52.  This  has  the  composition 
C2Cu2,  and  is  the  cuprous  salt  of  acetylene.  It  is  a  reddish- 
brown  substance,  insoluble  in  water.  When  dry,  it  explodes 
violently  at  120°.  Hydrochloric  acid  decomposes  it,  acetylene 
being  evolved. 

Experiment  53.  Filter  off  the  precipitate  obtained  in  Exp.  52, 
and  wash  it  until  the  wash-water  runs  through  colorless.  Bring  the 
precipitate,  together  with  a  little  water,  into  a  flask  furnished  with  a 
funnel-tube  and  a  delivery-tube.  Slowly  add  concentrated  hydrochloric 
acid,  and  notice  the  evolution  of  gas.  Collect  some  of  it  in  a  small 
cylinder  over  water,  and  burn  it. 

Acetylene  acts  like  a  weak  dibasic  acid.  Cuprous  carbide, 
C2Cu2,  calcium  carbide,  C2Ca,  silver  carbide,  C2Ag2,  etc.,  are 
salts  of  the  acid. 

Calcium  carbide,  CaC2,  is  formed  by  heating  coal  and  lime 
together  in  the  electric  furnace.  With  water  it  gives  acetylene 
and  calcium  hydroxide.  It  is  used  extensively  for  illuminat- 
ing purposes. 

Acetylene  unites  with  bromine,  forming  the  compound 
C2H2Br4,  tetra-brom-ethane.  It  unites  with  hydrobromic  and 
hydriodic  acids,  forming  substitution-products  of  the  saturated 
hydrocarbons:  — 


The  union  between  the  carbon  atoms  in  acetylene  is  com- 
monly  represented  by   three  lines   (=),   or   three    dots   (•). 


ACETYLENE  249 

CH 

Thus,  acetylene  is  written  III     or  CHJCH.      Like  the   sign   of 

CH 

the  ethylene  condition,  the  sign  of  the  acetylene  condition 
should  not  be  interpreted  too  literally.  It  is  best  to  regard  it 
as  the  sign  of  the  condition  existing  in  acetylene.  TJiis  condi- 
tion carries  with  it  the  power  to  take  up  four  atoms  of  a  halogen, 
or  two  molecules  of  hydrobromic  acid  and  similar  acids,  and  to 
form  metallic  derivatives  like  those  of  acetylene  above  referred  to. 
Most  of  the  higher  members  of  the  acetylene  series  of  hydro- 
carbons bear  to  acetylene  the  same  relation  that  the  higher  mem- 
bers of  the  ethylene  series  bear  to  ethylene.  The  first  one  is 

Allylene  or  methyl-acetylene  .  .  .  CH3.C:CH; 
the  second  is 

Ethyl-acetylene C2H5.C;CH, 

or  Dimethyl-acetylene CH3.C:C.CH3. 

It  should  be  noticed  in  this  connection  that  there  is  a  hydro- 
carbon ot  the  formula  C4H6,  which,  strictly  speaking,  is  not 
a  homologue  of  acetylene,  though  it  is  closely  related  to 

CH:CH2 
dimethyl-acetylene.     It  has  the  formula  I 

CH:CH2 

The  homologues  of  acetylene  may  be  divided  into  two  classes: 

1.  Those  which  are  obtained  from  acetylene  by  the  replace- 
ment  of  one  or  both   of  the  hydrogen   atoms   by   saturated 
radicals,  such  as  methyl,  ethyl,  etc.     These  are  called  the  true 
homologues.    They  all  retain  the  condition  peculiar  to  acetylene. 

2.  Those  in  which  the  ethylene  condition  occurs  twice,  as 
in  the  hydrocarbons  of  the  formulas 

C(CH3) 


CH:CH2 

These  may  be  called  diethylene  derivatives.     These,  like  acety- 
lene and  its  true  homologues,  have  the  power  to  take  up  four 


250       UNSATURATED  CARBON  COMPOUNDS 

atoms  of  a  halogen,  or  two  molecules  of  hydrobromic  acid  and 
similar  acids,  but  they  do  not  form  copper  and  silver  salts. 

Propargyl  alcohol,  C3H4O.  —  This  alcohol  is  mentioned 
merely  as  an  example  of  alcohols  which  are  derived  from  the 
acetylene  hydrocarbons.  It  is  the  hydroxyl  derivative  of 
allylene,  or  methyl-acetylene.  It  is  made  by  treating  brom- 
allyl  alcohol,  C3H4Br.OH,  with  alcoholic  caustic  potash:  — 

CH2OH  CH2OH 

|  =  |  +  HBr. 

CBr  =  CH2      C  =  CH 

ACIDS,  CnH2n_402 

These  acids  are  the  carboxyl  derivatives  of  the  acetylene 
hydrocarbons,  and  hence  differ  from  the  members  of  the  acrylic 
acid  series  by  two  atoms  of  hydrogen  each,  and  from  the  mem- 
bers of  the  fatty  acid  series  by  four  atoms  of  hydrogen  each. 

/CH          N 
Propiolic  acid,  CsHaOaf  III  ).  —  The  potassium  salt  of 


this  acid  has  been  made  from  the  acid  potassium  salt  of  acety- 

C.C02K 
lene-dicarbonic  acid,  |||          ,  by  heating  its  aqueous  solution. 

C.C02H 

Acetylene-dicarbonic  acid  is  formed  by  heating  dibrom-succinic 
acid  with  a  water  solution  of  caustic  potash  :  — 

CHBr.C02H      C.C02H 

|  =|||  +  2HBr. 

CHBr.C02H      C.CO.H 

/C.CH3    \ 
Tetrolic  acid,  C4H4OJ  |||  ),  is  obtained  by  treating 

\C.CO2H/ 
/3-chlor-crotonic  acid  with  caustic  potash:  — 

CC1.CH,         C.CH3 

II  =  III  4-HCL 

CH.CO.H      C.CO.H 


VALYLENE  251 

Sorbic    acid,   C6H8O2(CH3  .CH:CH.  CH  :CH  .  CO2H).  - 

This  acid  occurs  in  the  juice  of  the  unripe  sorb  apple.  It 
takes  up  hydrogen  and  yields  hydrosorbic  acid,  a  member  of 
the  acrylic  acid  series  (see  table,  p.  238).  It  also  takes  up 
bromine,  the  final  product  of  the  action  being  an  acid  of  the 
formula  C5H7Br4.C02H.  With  hydrobrornic  acid  it  forms 
dibrom-caproic  acid  :  — 

C5H7  .  C02H  +  2  HBr  =  C5H9Br2.  C02H. 

Dibrom-caproic  acid 

It  will  be  observed  that  sorbic  acid  is  a  diethylene  derivative 
and  that  it  does  not  contain  the  acetylene  condition. 


Linoleic  acid,  dgHszC^CCnH^COaH).  —  This  acid  occurs 
in  the  form  of  an  ethereal  salt  of  glycerol  in  drying  oils.  It 
can  be  obtained  from  linseed  oil  by  saponification.  It  is  an 
oily  liquid,  one  of  the  most  marked  properties  of  which  is  its 
power  to  take  up  oxygen  from  the  air,  and  turn  into  a  solid 
substance.  Linseed  oil  itself  has  this  property  of  hardening 
or  drying.  It  is  the  principal  substance  belonging  to  the  class 
of  drying  oils.  The  oil  is  used  extensively  as  a  constituent  of 
varnishes  and  of  oil  paints. 

The  relations  between  linoleic,  olei'c,  and  stearic  acids  as  far 
as  their  composition  is  concerned  are  shown  by  the  following 
formulas  :  — 

CisHgA  C18H3402  C18H3202 

Stearic  acid  Oleic  acid  Linoleic  acid 


Valylene,  C5H6.  —  We  have  thus  far  had  to  deal  with  three 
series  of  hydrocarbons  of  the  general  formulas  CnH2n+2,  CnH^, 
and  CnH2n_2.  We  naturally  inquire  whether  there  is  a  series  of 
the  general  formula  CnH2n_4.  A  few  members  of  the  series  have 
been  prepared  by  abstracting  hydrogen  from  certain  of  the 
acetylene  hydrocarbons  by  the  action  of  alcoholic  potash  on  the 


252       UNSATURATED  CARBON  COMPOUNDS 

bromine  derivatives.     Thus,  valylene,  C5H6,  has  been  made  by 
treating  valerylene  bromide,  C5H8Br2,  with  alcoholic  potash  :  — 


It  is  a  liquid.  Its  most  characteristic  property  is  its  power 
to  unite  with  bromine  to  form  the  saturated  compound  C5H6Br6. 

Dipropargyl,  C6H6-  —  Dipropargyl  (boiling  point  85°)  is 
obtained  from  the  compound  diallyl-tetrabromide,  CgH^Br^  by 
boiling  with  alcoholic  caustic  potash  :  — 

C6H10Br4==C6H6  +  4HBr. 

It  unites  very  readily  with  bromine,  forming,  as  the  final 
product  of  the  action,  the  compound  C6H6Br8,  which  is  an  octo- 
bromine  substitution-product  of  hexane,  C6H14. 


The  unsaturated  hydrocarbons  and  their  derivatives  thus  far 
treated  of  are  obtained  by  simple  reactions  from  the  saturated 
compounds,  and  they  all  have  the  power  to  take  up  bromine, 
hydrobromic  acid,  etc.,  readily,  and  thus  to  pass  back  to  the 
saturated  condition.  Whatever  the  real  nature  of  the  relation 
between  the  carbon  atoms  in  all  these  unsaturated  hydrocarbons 
may  be,  it  is  easily  changed  to  the  condition  that  exists  in  the 
saturated  compounds.  There  are  several  hydrocarbons,  how- 
ever, which  are  unsaturated  but  are  not  easily  converted  into 
derivatives  of  the  saturated  hydrocarbons.  Although  under 
some  circumstances  they  with  difficulty  combine  directly  with 
the  halogens,  they  do  not  take  up  enough  to  convert  them  into 
derivatives  of  the  paraffins ;  and  the  products  formed  are  un- 
stable, easily  giving  up  the  halogen  atoms  with  which  they 
combined.  The  simplest  hydrocarbon  of  this  kind  is  the  well- 
known  benzene,  which  is  isomeric  with  dipropargyl.  Before 
proceeding  to  the  study  of  benzene  and  its  derivatives,  it  will 
be  well  to  inquire  whether  the  abstraction  of  hydrogen  by 
the  reaction  chiefly  used  can  be  pushed  further  than  it  has 
thus  far  been  pushed.  Can  we,  in  other  words,  by  means  of 
this  reaction  get  hydrocarbons  of  the  formula  CnH2n_8  which 


UNSATURATED  HYDROCARBONS          253 

have  the  power  to  unite  directly  with  ten  atoms  of  bromine  ? 
Such  hydrocarbons  have  not  been  prepared.  Hydrocarbons  of 
the  formula  CnH2n_8  are  known;  but  they  are  not  made  from 
the  paraffins  by  abstracting  hydrogen,  and  they  are  not  con- 
verted  into  substitution-products  of  the  paraffins  by  the 
addition  of  halogens  and  halogen  acids. 

The  compounds  which  have  been  treated  of  fall  under  five 
general  heads,  according  to  the  formulas  of  the  hydrocarbons. 
These  heads  are  :  — 

1.  Hydrocarbons,  CnH2n+2,  the  paraffins  and  their  derivatives. 

2.  Hydrocarbons,  C^H^,    or  olefins  and  their  derivatives. 

3.  Hydrocarbons,  CnH.2a_2)  or  the   acetylene    hydrocarbons    and 

their  derivatives. 

4.  Hydrocarbons,  CnH^^,  and  their  derivatives. 

5.  Hydrocarbons,  CJJ.^^,  and  their  derivatives. 


This  classification,  while  strictly  correct,  is  misleading,  inas- 
much  as  it  conveys  no  idea  in  regard  to  the  relative  importance 
of  the  compounds  of  the  different  classes.  As  we  have  seen,  the 
only  compounds  whose  treatment  required  much  space  are  those 
of  the  first  class.  These  compounds  stand  out  prominently, 
and  are  distinguished  by  the  frequency  of  their  occurrence  and 
their  great  number.  The  compounds  of  the  second  class  are 
much  less  numerous,  and  but  a  small  number  of  them  are  familiar 
substances.  While  a  few  substances  belonging  to  the  third 
class  are  known,  our  knowledge  in  regard  to  the  class  is  much 
more  limited  than  even  that  of  the  second  class.  Finally,  as 
regards  the  fourth  and  fifth  classes,  the  few  representatives 
of  them  that  are  known  are  at  present  scientific  curiosities. 
Thus,  after  we  leave  the  paraffin  derivatives,  our  knowledge 
dwindles  away  very  rapidly  when  we  pass  to  the  following 
classes,  until  it  ends  with  a  single  compound  in  the  fifth  class. 

Let  us  now  pass  to  the  consideration  of  a  new  group,  the 
importance  and  number  of  whose  members  entitle  it  to  rank 
with  the  group  of  paraffin  derivatives. 


CHAPTER   XIV 

THE    BENZENE    SERIES  OF    HYDROCARBONS.— 
AROMATIC  COMPOUNDS 

THE  fundamental  substance  of  this  group  is  benzene,  C6H6, 
which,  bears  to  the  group  the  same  relation  that  marsh  gas 
bears  to  the  group  of  paraffin  derivatives.  Benzene,  together 
with  some  of  its  homologues,  is  a  product  of  the  distillation  of 
bituminous  coal,  and  is,  therefore,  contained  in  coal  tar.  As 
coal  tar  is  the  raw  material  from  which  all  benzene  derivatives 
are  obtained,  it  will  be  well  briefly  to  describe  the  conditions 
of  its  formation  and  the  method  of  obtaining  pure  hydrocar- 
bons from  it. 

Coal  tar  is  a  thick,  black,  tarry  liquid,  which  is  obtained  in 
the  manufacture  of  illuminating  gas  from  bituminous  coal. 
The  coal  is  heated  in  retorts,  and  all  the  products  passed 
through  a  series  of  tubes  called  condensers.  These  are  kept 
cool,  and  in  them  the  liquid  and  volatile  solid  products  are  con- 
densed, forming  together  the  coal  tar.  It  is  an  extremely  com- 
plex mixture,  from  which  a  great  many  substances  have  been 
obtained.  Among  those  most  readily  obtained  from  it  are  the 
hydrocarbons  of  the  benzene  series,  as  well  as  the  hydrocarbons 
naphthalene  and  anthracene,  both  of  which  are  important  sub- 
stances. 

When  the  tar  is  heated,  of  course  the  most  volatile  liquids 
pass  over  first.  These  are  collected  in  vessels  containing  water. 
The  first  portions  of  the  distillate  float  on  water,  and  constitute 
what  is  called  the  light  oil.  After  a  time  hydrocarbons  and 
other  substances  of  greater  specific  gravity  than  the  light  oil 
pass  over.  These  portions  sink  under  water,  and  constitute 
the  heavy  oil. 

254 


BENZENE   SERIES  255 

The  light  oil  is  treated  with  caustic  soda,  which  removes 
phenol  (carbolic  acid)  and  similar  substances,  and  with  sul- 
phuric acid,  which  removes  certain  basic  compounds  and  olefins. 
The  residue  is  then  subjected  to  fractional  distillation,  by 
which  means  the  first  two  members  of  the  series  can  be  ob- 
tained in  very  nearly  pure  condition.  As  these  hydrocarbons 
form  the  basis  of  a  number  of  important  industries,  they  are 
separated  from  coal  tar  on  the  large  scale. 

The  principal  members  of  the  series  are  named  in  the  table 
below 

HYDROCARBONS,  CJI^^ 

BENZENE  SERIES 

Benzene C6H6. 

Toluene C7Hg. 

Xylenes C8H10. 

Mesitylene        ] 
Pseudocumene  j 
Durene 
Cymene 
Hexa-methyl  benzene . 


}.....        ....    C10H14. 


Benzene,  C6H6.  —  Benzene  is  prepared,  as  above  described, 
from  the  light  oil  obtained  from  coal  tar.  A  large  part  of  the 
benzene  now  used  is  obtained  from  the  gas  formed  in  the  coke 
furnaces.  It  is  also  prepared  by  heating  benzoic  acid  with  lime, 
when  the  acid  breaks  up  into  carbon  dioxide  and  benzene:  — 

C7H602  =  C6H6+ C02. 

NOTE  FOR  STUDENT.  —  What  is  the  analogous  method  for  the  prepara- 
tion of  marsh  gas  ? 

Benzene  has  been  made  further  by  simply  heating  acetylene :  — 

3  C2H2  =  C6H6. 
To  purify  the  hydrocarbon  obtained  by  fractional  distillation 


256       BENZENE  SERIES  OF  HYDROCARBONS 

from  light  oil,  it  is  cooled  down  to  a  low  temperature,  and  that 
which  does  not  solidify  is  poured  off.  The  crystals  aro  pressed 
in  the  cold  between  layers  of  bibulous  paper,  and  are  then  very 
nearly  pure  benzene.  This  can  be  further  purified  by  treat- 
ment with  sulphuric  acid,  which  removes  a  small  quantity  of  a 
substance  containing  sulphur,  and  known  as  thiophene,  C4H4S. 
Perfectly  pure  benzene  is  obtained  by  distilling  pure  benzoic 
acid  with  lime. 

Experiment  54.  Mix  intimately  50s  benzoic  acid  and  100*  quick- 
lime, and  distil  from  a  retort  connected  with  a  condenser.  See  that  the 
materials  and  apparatus  are  dry.  Add  a  little  calcium  chloride  to  the 
distillate ;  and,  after  it  has  stood  for  an  hour  or  two,  redistil  it  from  a 
distilling-bulb  of  proper  size,  noting  the  temperature  at  which  it  boils. 
Put  the  redistilled  hydrocarbon  in  a  test-tube,  and  surround  it  with  a 
freezing  mixture. 

Experiment  55.  In  some  places  where  there  are  gas-works  it  is 
possible  to  procure  a  quantity  of  light  oil.  The  separation  of  some 
of  this  into  benzene  and  toluene,  and  the  purification  of  the  two  hydro- 
carbons, is  the  best  possible  introduction  to  a  study  of  the  aromatic 
compounds.  The  benzene  and  toluene  thus  obtained  may  be  used  in  the 
preparation  of  a  number  of  typical  derivatives  according  to  methods 
which  will  be  described.  In  fractioning  the  light  oil,  it  will  be  observed 
that  there  is  a  tendency  to  an  accumulation  of  the  distillates  in  the  parts 
boiling  near  80.5°  (the  boiling-point  of  benzene)  and  110°  (the  boiling- 
point  of  toluene).  The  final  purification  of  the  benzene  should  be  effected 
by  freezing  and  pressing,  as  described  above.  The  toluene  should  be  dis- 
tilled until  its  boiling-point  is  not  changed  by  redistillation.  , 

Benzene  is  a  colorless  liquid  boiling  at  80.5°.  It  has  a 
peculiar,  pleasant  odor.  Several  of  the  homologues  of  benzene 
have  a  similar  odor.  Hence  the  name  aromatic  compounds  was 
given  to  them  originally,  and  it  is  still  in  general  use.  Ben- 
zene is  lighter  than  water,  its  specific  gravity  being  0.899  at  0°. 
It  is  insoluble  in  water,  soluble  in  alcohol  and  chloroform.  It 
burns  with  a  bright,  luminous,  smoky  flame. 

Experiment  56.  Pour  a  layer  of  benzene  on  water  in  a  small 
•vaporating-dish.  Set  fire  to  it. 


BENZENE   SERIES  257 

Benzene  crystallizes  in  orthorhombic  prisms  when  cooled  to 
0°.  These  melt  at  6°.  It  is  an  excellent  solvent  for  oily  and 
resinous  substances.1 

Chemical  conduct  of  benzene,  and  hypothesis  regarding  its 
structure.  In  the  light  of  the  knowledge  already  gained  in 
studying  hydrocarbons  which  contain  a  smaller  proportion  of 
hydrogen  than  the  paraffins,  we  should  naturally  expect  to  find 
that  benzene  can  easily  be  converted,  into  a  derivative  of 
hexane.  We  should  expect  to  find  that  it  unites  with  bromine, 
just  as  dipropargyl  does,  to  form  an  octo-brom-hexane  thus,  — 


with  hydrobromic  acid  to  form  tetra-brom-hexane  thus,  — 


and  probably  with  hydrogen  to  form  hexane,  — 
CgHg  -f-  8  H  =  C6H14. 

But  none  of  these  reactions  takes  place.  Hydrobromic  acid, 
which  combines  so  readily  with  all  the  unsaturated  compounds 
hitherto  considered,  does  not  act  at  all  upon  benzene.  Bromine 
acts  readily  enough,  but  the  action  which  usually  takes  place 
is  like  that  which  takes  place  with  the  saturated  paraffins.  It 
is  substitution,  and  not  addition.  Thus,  bromine  forms  mono- 
brom-benzene,  C6H5Br,  under  ordinary  circumstances.  If, 
however,  the  action  takes  place  in  the  direct  sunlight,  a 
product  is  formed  which  has  the  formula  C6H6Br6,  known  as 
benzene  hexdbromide,  and  to  this  no  more  bromine  can  be  added. 

Benzene  takes  up  six  atoms  of  hydrogen  and  yields  a  hydro- 
carbon of  the  composition  C6H12.  This  is  not  a  member  of  the 
ethylene  series.  (See  Hexamethylene.) 

The  facts  mentioned  show  clearly  that  benzene  differs  in 
some  way  fundamentally  from  all  the  hydrocarbons  which 

1  Benzene,  the  chemical  individual  of  the  definite  formula  C6H6,  must  not  be  confounded 
with  "benzine,"  the  commercial  substance  obtained  in  the  refining  of  petroleum  (see  p, 


258  BENZENE   SERIES    OF    HYDROCARBONS 

have  been  treated  of  thus  far.  But  these  facts  are  not  suffi- 
cient to  enable  us  to  form  an  hypothesis  in  regard  to  its  struc- 
ture. On  studying  the  many  substitution-products  of  benzene, 
however,  facts  of  a  different  order  and  of  the  highest  impor- 
tance are  revealed. 

It  will  be  remembered  that  the  theory  in  regard  to  the  rela- 
tions of  the  paraffins  to  each  other  is  based  upon  the  fact,  that 
only  one  mono-substitution  product  of  marsh  gas  can  be  ob- 
tained with  any  given  substituting  agent.  There  is  but  one 
chlor-methane,  but  one  brom-methane,  etc.  This  fact  leads  to 
the  belief  that  each  hydrogen  atom  of  marsh  gas  bears  the 
same  relation  to  the  carbon  atom,  or  that  marsh  gas  is  a  sym- 
metrical compound.  A  similar  conclusion  has  been  reached 
in  regard  to  benzene;  and  it  is  based  upon  a  thorough 
study  of  the  substitution-products.  Notwithstanding  almost 
innumerable  efforts  to  prepare  isomeric  mono-substitution 
products  of  benzene,  no  such  isomeric  substances  have  been 
prepared.  There  is  but  one  mono-brom-benzene,  but  one  mono- 
chlor-benzene,  etc.  Further,  mono-brom-benzene  has  been  pre- 
pared by  substituting  bromine  for  each  of  the  six  hydrogen 
atoms  of  benzene  successively ;  and  the  product  has  been  found 
to  be  the  same,  no  matter  which  hydrogen  is  replaced.  As  this 
fact  is  of  fundamental  importance,  it  will  be  well  to  point  out 
how  it  is  possible  to  replace  the  six  hydrogens  successively,  and 
to  know  that  in  each  case  a  different  hydrogen  atom  is  replaced. 
While  it  would  lead  too  far  to  follow  this  subject  in  detail,  the 
principle  involved  can  be  made  clear  in  a  few  words :  — 

We  have  a  compound,  the  formula  of  which  is  C6H6.     Write 

123456 

it  thus,  C6HHHHHH,  numbering  the  hydrogen  symbols  to  fa. 

i 
cilitate  reference  to  them.     The  problem  is  to  replace,  say  H, 

»  2 

by  bromine ;  in  a  second  case,  to  replace  H  by  bromine ;  in  a 

third,  H,  etc. ;  and  to  compare  the  six  mono-brom-benzenes  thua 
obtained.  Suppose  we  treat  benzene  with  bromine.  We  get 


BENZENE   SERIES  259 

a  mono-brom-benzene,  and  we  know  that  one  of  the  hydrogen 
atoms  is  replaced  by  bromine,  but  of  course  we  cannot  tell 
which  one.  We  may  assume  that  it  is  any  one  of  the  six 
represented  in  the  above  formula.  For  the  sake  of  the  argu- 

1  23456 

ment,  call  it  H.  Our  compound  is  therefore  C6BrHHHHH. 
Now  treat  this  compound  with  something  else  which  has  the 
power  to  replace  the  hydrogen,  say  nitric  acid.  A  second 
hydrogen  atom  is  replaced  by  the  nitro  group  ]ST02.  Again, 
we  do  not  know  which  one  of  the  hydrogen  atoms  is  replaced 
in  this  operation,  but  we  do  know  that  it  is  a  different  one 
from  that  which  was  replaced  by  the  bromine  in  the  first 

operation.     Call   it   H.     We  have,   therefore,   the   compound 

3456 

C6Br(N02)HHHH.  By  treating  this  compound  with  nascent 
hydrogen,  two  reactions  take  place,  the  chief  one  for  our 
present  purpose  being  the  replacement  of  the  bromine  by 

hydrogen.     In   other   words,   H  is   put  back   into   the  com- 

1  3456 

pound  again,  and  we  have  C6H(NH2)HHHH.  By  means 
of  two  reactions  which  will  be  studied  farther  on  it  is  a 
simple  matter  to  replace  the  amino  group  by  bromine.  This 

1  3456 

done,  we  have  the  compound  C6HBrHHHH,  or  a  mono-brom- 
benzene,  in  which  the  bromine  certainly  replaces  a  different 
hydrogen  atom  from  that  replaced  by  direct  substitution.  The 
two  products  are,  however,  identical.  The  above  explanation 
will  serve  to  make  clear  the  principle  that  is  involved  in  the 
study  of  the  relations  which  the  hydrogen  atoms  contained  in 
benzene  bear  to  the  molecule.  The  principle  has  been  applied 
successively  to  all  the  hydrogen  atoms,  and,  as  already  stated, 
the  result  is  the  proof  that  all  these  hydrogen  atoms  bear  the 
same  relation  to  the  molecule.  The  same  is  true  of  the  carbon 
atoms,  as  the  compound  is  symmetrical. 

How  can  we  imagine  six  carbon  atoms  and  six  hydrogen 
atoms  arranged  so  that  all  these  shall  bear  the  same  relation 
to  the  molecule  ?  The  simplest  conception  is  that  each  carbon 


260  BENZENE   SERIES    OF   HYDROCARBONS 

is  in  combination  with  one  hydrogen,  and  that  the  six  carbon 
atoms  are  arranged  in  the  form  of  a  ring,  and  not,  as  in  the 
paraffins,  in  the  form  of  an  open  chain,  or  a  chain  with  branches. 
Using  our  ordinary  method  of  representation,  this  conception 
is  symbolized  in  the  formula 

H 

G 

H(y  \3H 

Hcl  yen 

^c^ 

H 

or,  as  the  curved  lines  have  no  special  significance,  the  expres- 
sion becomes 

H 

HC/  \CH 


H 

This  symbol,  then,  is  the  expression  of  a  thought  suggested  by 
a  study  of  the  chemical  conduct  of  benzene.  Before  we  can 
accept  it  as  probable,  it  must  be  tested  by  all  the  facts  known 
to  us.  If  it  is  not  in  accordance  with  all  of  them,  if  it  sug- 
gests possibilities  which  are  not  realized,  then  it  must  be  dis 
carded. 

In  the  first  place,  then,  does  it  account  for  the  addition 
products,  benzene  hexabromide,  hexa-hydro-benzene,  etc.?  The 
formula  represents  each  carbon  atom  as  trivalent,  and  we  should 
expect,  therefore,  each  one  to  have  the  power  to  take  up  an 
additional  univalent  atom,  forming,  in  the  case  of  bromine, 
a  compound  of  the  formula 


BENZENE  261 

HBr 

BrHC/  \CHBr 

I  I 

BrHCv        /CHBr 
XJ/ 

HBr 

in  which  each  carbon  atom  is  acting  as  a  quadrivalent  atom. 
Unless  the  ring  form  of  combination  between  the  carbon  atoms 
is  broken  up,  it  is  impossible  for  the  compound  to  take  up 
more  bromine.  Hence,  the  last  product  of  the  addition  of 
bromine  to  benzene  should  be  benzene  hexabromide.  The 
facts  and  the  hypothesis  are  in  harmony. 

Again,  we  may  inquire  :  Of  how  many  isomeric  di-substitu- 
tion  products  of  benzene  does  the  hypothesis  suggest  the  exist- 
ence ?  Numbering  the  hydrogens  in  the  formula,  we  have  :  — 

;V-      «g 

(6)H(X      X)H(2) 


H(4) 

The  hydrogens  (1)  and  (2),  (2)  and  (3),  (3)  and  (4),  (4)  and 
(5),  (5)  and  (6),  and  (6)  and  (1),  bear  the  same  relations  to 
each  other  ;  and,  according  to  the  formula,  whether  we  replace 
(1)  and  (2),  or  (2)  and  (3),  or  (3)  and  (4),  or  any  other  of  the 
above-named  pairs,  the  product  ought  to  be  the  same.  We 
should  get  a  compound  of  which  the  following  is  the  general 
expression,  in  which  X  represents  any  substituting  atom  or 
group:—  x 

HC/  \CX 

I  I 

HCV      yCH 

XX 

H 

Formula  I. 


262  BENZENE   SEEIES   OP   HYDROCARBONS 

In  the  second  place,  the  hydrogens  (1)  and  (3),  (2)  and  (4), 
(3)  and  (5),  (4)  and  (6),  (5)  and  (1),  and  (6)  and  (2)  bear  to 
each  other  the  same  relation,  but  a  different  relation  from 
that  which  the  above  pairs  do.  Replacing  any  such  pair,  we 
should  have  a  second  compound,  which  is  represented  by  the 
general  formula 

X 

HC/  \CH 


H 

Formula  II. 


Finally,  there  is  a  third  kind  of  relation,  which  is  that 
between  hydrogens,  (1)  and  (4),  (2)  and  (5),  and  (3)  and  (6)  ; 
and,  by  replacing  such  a  pair,  we  should  get  a  compound 
represented  by  the  general  formula 


HC/  \CH 

I  I 

HC  CH 


X 

Formula  III. 

The  hypothesis  suggests  no  other  possibilities.  We  see  thus 
that  the  hypothesis  indicates  the  existence  of  three,  and  only 
three,  classes  of  di-substitution  products  of  benzene.  There 
ought  to  be  three,  and  only  three,  di-chlor-benzenes  ;  three, 
and  only  three,  di-brom-benzenes,  etc. 

The  di-substitution  products  have  been  studied  very  ex- 
haustively for  the  purpose  of  determining  definitely  whether 
the  conclusion  above  reached  is  in  accordance  with  the  facts  ; 
and  it  may  be  said  at  once,  that  every  fact  thus  far  discovered 
is  in  harmony  with  the  hypothesis.  Three  well-marked  classes 


BENZENE 


263 


of  isomeric  di-substitution  products  of  benzene  are  known,  and 
only  three  ;  and  many  representatives  of  the  three  classes  have 
been  studied  carefully.  There  are  many  other  facts  of  less 
importance  known  which  furnish  arguments  in  favor  of  the 
benzene  hypothesis  expressed  in  the  formula  above  discussed, 
but  this  is  not  the  place  to  discuss  them.  Let  it  suffice,  for 
the  present,  to  recognize  that  the  hypothesis  is  in  accordance 
with  the  most  important  facts  known  to  us. 

There  is  one  point  that  has  not  been  touched  upon,  and  that 
is  the  relation  of  the  carbon  atoms  to  each  other.  The  formula 
is  commonly  written  thus :  — 

H 

r1 

HC^  \CH 

I  II 

HCL     /CH 

XX 

H 

which  indicates  that  the  carbon  atoms  are  joined  together  alter- 
nately by  single  and  by  double  bonds.     This  formula,  however, 
expresses  something  about  which  we  know  little,  and  concern- 
ing which  it  is  difficult,  at  present,  to  form  any  conception. 
Another  formula  that  has  been  suggested  is  this :  — 

CH 


CH 


CH 


In  each  of  these,  as  will  be  seen,  an  attempt  is  made  to  account 
for  the  fourth  bond  of  each  carbon  atom.  The  question  in- 
volved is  an  extremely  difficult  one  to  investigate,  and  it  is 
not  surprising  that  chemists  do  not  agree  as  to  the  formula 
to  be  preferred. 


264  BENZENE   SERIES    OF    HYDROCARBONS 

The  simple  formula 


J.J. 

HO/  \J 

I  ! 


H 

H 


H 

leaves  the  question  as  to  the  relation  between  the  carbon  atoms 
entirely  open,  and  suffices  for  most  purposes. 

The  benzene  hypothesis  has  been  treated  of  somewhat  fully, 
for  the  reasons,  that  it  has  played  an  extremely  important  part 
in  the  study  of  the  benzene  derivatives,  and  that  its  use  serves 
greatly  to  simplify  the  study  of  these  derivatives. 

Benzene  and  its  homologues  form  nitro  compounds  arid  sul- 
phonic  acids  by  direct  treatment  with  nitric  and  sulphuric 
acids,  respectively.  This  distinguishes  them  from  the  paraffins 
and  other  hydrocarbons  hitherto  treated  of. 

Toluene,  C7H8(C6H5.CH3).—  Toluene  was  known  before 
it  was  obtained  from  coal  tar,  as  it  is  formed  by  the  dry  dis- 
tillation of  Tolu  balsam,  whence  its  name.  Its  relation  to 
benzene  is  shown  by  its  synthesis  from  brom-benzene  and 
methyl  iodide  :  — 

C6H5Br  +  CH3I  +  Na,  =  C6H5  .  CH3  +  NaBr  +  Nal. 

According  to  this  synthesis,  toluene  appears  as  methyl-benzene, 
or  benzene  in  which  one  hydrogen  is  replaced  by  methyl  ;  or 
as  phenyl-methane,  or  methane  in  which  one  hydrogen  atom  is 
replaced  by  the  radical  phenyl,  C6H5,  which  bears  the  same 
relation  to  benzene  that  methyl  bears  to  marsh  gas. 

Toluene  is  a  colorless  liquid  that  boils  at  110°  ;  it  has  the 
specific  gravity  0.8824  at  0°  ;  and  has  a  pleasant  aromatic  odor. 

It  is  very  susceptible  to  the  action  of  reagents,  yielding  a 
large  number  of  substitution-products,  some  of  the  most  im- 
portant of  which  will  be  taken  up  farther  on. 


XYLENES  265 

But  one  toluene  or  methyl-benzene  has  ever  been  dis- 
covered. 

Towards  oxidizing  agents  its  conduct  is  peculiar  and  inter- 
esting. The  methyl  is  oxidized,  while  the  phenyl  remains 
intact.  The  product  is  a  well-known  acid,  benzoic  acid,  which, 
as  we  have  seen,  breaks  up  readily  into  carbon  dioxide  and 
benzene.  It  has  the  composition  C7H602,  and  is  the  carboxyl 
derivative  of  benzene,  C6H5.C02H.  The  oxidation  of  toluene 
is  represented  by  the  equation 

C6H5.CH3  +  30  =  C6H5.C02H  +  H2O. 

Xylenes,  C8H10[C6H4(CH3)2].  —  That  portion  of  light  oil 
which  boils  at  about  140°  was  originally  called  xylene.  It  was 
afterwards  found  that  this  coal-tar  xylene  consists  of  three 
isomeric  hydrocarbons.  As  the  boiling-points  of  these  three 
substances  lie  quite  near  together,  it  is  impossible  to  separate 
them  by  means  of  fractional  distillation.  By  treatment  with 
sulphuric  acid,  however,  they  can  be  separated,  and  thus  ob- 
tained in  pure  condition.  They  are  known  as  ortho-xylene, 
meta-xylene ,  and  parorxylene. 

Ortho-xylene  resembles  benzene  and  toluene  in  its  general 
properties,  but  boils  at  142°. 

Meta-xylene  boils  at  137°,  It  is  the  principal  constituent 
of  commercial  xylene. 

Para-xylene  boils  at  136°  to  137a. 

These  hydrocarbons  have  also  been  obtained  from  toluene 
by  means  of  the  reaction  made  use  of  for  the  purpose  of  con 
verting  benzene  into  toluene. 

Another  method  that  is  of  value  for  the  preparation  of  the 
homologues  of  benzene  consists  in  treating  benzene  with  a  halo- 
gen derivative  of  another  hydrocarbon  in  the  presence  of 
aluminium  chloride  (see  p.  363). 


266       BENZENE  SERIES  OF  HYDROCARBONS 

This  shows  that  they  are  all  methyl-toluenes.  There  are 
three  mono-brom-toluenes,  known  as  ortho-,  meta-,  and  para- 
brom-toluene.  For  the  preparation  of  ortho-xylene,  ortho- 
brom-toluene  is  used;  meta-brom-toluene  yields  meta-xylene, 
and  para-brom-toluene  yields  para-xylene. 

Ortho-  and  meta-xylene  have  also  been  obtained  from  certain 
acids,  which  bear  to  them  the  same  relation  that  benzoic  acid 
bears  to  benzene  :  — 

rcH3 

C6H  J  CH3     =  C6H4(CH3)2  +  CO* 
IC02H 

The  reaction  by  which  meta-xylene  is  formed  from  mesitylenic 
add  is  of  special  importance,  as  will  be  pointed  out. 

By  oxidation,  the  xylenes  undergo  changes  like  that  which 
is  illustrated  in  the  formation  of  benzoic  acid  from  toluene, 
consisting  in  the  transformation  of  methyl  into  carboxyl. 

/^TT 

The  first  change  gives  acids  of  the  formula  C6H4<nrk3_T,  one 

UL^ix 

corresponding  to  each  xylene.     By   further   oxidation,  these 
three  monobasic  acids  are  converted  into  dibasic  acids  of  the 

fO  FT 

formula  C6H4<C02H.     Thus,  we  have  the  three  reactions,  all 
of  the  same  kind:  — 

(1)  C6H5.CH3       +30  =  C6H5.C02H    +  H20; 

PTT  PTT 

(2)  C6H4 


and       (3)C6H4 

f'TT 

The  three  monobasic  acids  of  the  formula  C6H4<      3    are 

002^1 

known  as  ortlio-toluic,  meta-toluic,  and  para-toluic  acids  re- 
spectively; and  the  three  dibasic  acids  obtained  from  them 
are  known  as  ortho-phthalic,  meta-phthalic,  and  para-phthalic 
acids.  Starting  thus  with  the  three  brom-toluenes,  we  get, 


XYLENES  267 

first,  three  xylenes,  then  three  toluic  acids,  and  finally  three 
phthalic  acids.  In  each  case,  we  distinguish  between  the 
three  isomeric  compounds  by  the  prefixes  ortho,  metaj  and 
para.  In  a  similar  way,  all  di-substitution  products  of  ben- 
zene are  designated.  We  therefore  have  three  series  into 
which  all  di-substitution  products  of  benzene  can  be  arranged ; 
and  these  are  known  as  the  Ortho-series,  the  Meta-series,  and 
the  Para-series.  In  arranging  them  in  this  way,  we  may 
select  any  prominent  di-substitution  product,  and  call  it  an 
ortho  compound;  and  then  call  one  of  its  isomerides  a  meta 
compound,  and  the  other  a  para  compound.  Having  thus  a 
representative  of  each  of  the  three  classes,  the  remainder  of 
the  problem  consists  in  determining  for  each  di-substitution 
product,  by  means  of  appropriate  reactions,  into  which  one 
of  the  three  representatives  it  can  be  transformed.  If  from 
a  given  compound  we  get  the  representative  of  the  ortho 
series,  we  conclude  that  the  compound  belongs  to  the  ortho 
series;  if  we  get  the  representative  of  the  meta  series,  we 
conclude  that  the  compound  is  a  ineta  compound;  and  if  we 
get  the  representative  of  the  para  series,  we  conclude  that 
the  compound  is  a  para  compound.  As  representatives,  we 
may  select  either  the  three  xylenes  or  the  three  phthalic  acids. 
Now,  to  repeat,  any  di-substitution  product  of  benzene  which 
can  be  converted  into  ortho-xylene  or  into  ortho-phthalic  acid 
is  regarded  as  an  ortho  compound,  etc. 

This  classification  of  the  di-substitution  products  of  benzene 
into  the  ortho,  meta,  and  para  series,  by  means  of  chemical 
transformations,  is  entirely  independent  of  any  hypothesis 
regarding  the  nature  of  benzene.  We  may  now  ask,  however, 
which  one  of  the  three  general  expressions  given  above  (see 
formulas  I.,  II.,  and  III.,  pp.  261,  262)  represents  the  relation 
of  the  groups  in  the  ortho  compounds,  which  one  the  relation 
in  the  meta  compounds,  and  which  one  the  relation  in  the  para 
compounds.  If  we  can  answer  these  questions  for  any  three 
isomeric  di-substitution  products,  the  answer  for  the  rest  will 


268  BENZENE   SERIES   OF   HYDROCARBONS 

follow.  To  reduce  the  problem  to  simple  terms,  therefore, 
let  us  take  the  three  xylenes.  We  have  three  xylenes  and 
three-  formulas  :  How  can  we  determine  which  particular  for- 
mula to  assign  to  each  xylene? 

As  may  be  imagined,  this  determination  is  by  no  means  a 
simple  matter;  and  it  has  been  the  occasion  of  a  great  many 
investigations.  Theoretically,  the  simplest  method  available 
consists  in  carefully  studying  the  substitution-products  of  each 
xylene,  to  discover  how  many  varieties  of  mono-substitution 
products  can  be  obtained  from  each.  The  formulas  are  :  — 

CH3  CH3  CH8 

(4)HCX  XC.CH3  (4)HC/  XCH(1)  (4)HC/  XCH(1) 
(3)HCX  /CH(1)  (3)HCX 


c  c 

H  H  ATT 

(2)  (2)  H» 

Formula  I.  Formula  II.  Formula  III. 

Each  of  the  four  benzene  hydrogens  of  the  xylene  of  for- 
mula III.  bears  the  same  relation  to  the  molecule.  It  there- 
fore should  make  no  difference  which  one  is  replaced,  the 
product  ought  to  be  the  same.  This  is  not  true  of  the  xylenes 
represented  by  formulas  I.  and  II.  That  xylene,  whose  struc- 
ture is  represented  by  formula  III.,  ought  therefore  to  yield 
but  one  kind  of  mono-substitution  product.  On  studying  the 
xylenes,  we  find  the  one  which  boils  at  136°  to  137°,  called 
para-xylene,  yields  but  one  kind  of  mono-substitution  products  ; 
that  is,  we  can  get  from  it  only  one  mono-brom-xylene  ;  only 
one  mono-nitro-xylene,  etc.  We  therefore  conclude  that  para- 
xylene  is  represented  by  formula  III.  above  ;  and,  further,  that 
formula  III.,  on  p.  262,  is  the  general  expression  for  all  para 
compounds. 

Examining  formula  I.  in  the  same  way,  we  see  that  H  (1) 
and  H  (4)  bear  the  same  relation  to  the  molecule;  and  that 


ETHYL-BENZENE  269 

H  (3)  and  H  (2)  also  bear  the  same  relation  to  the  molecule, 
though  different  from  that  of  H  (1)  and  H  (4).  Two  chlor- 
xylenes  of  the  formulas 

CH3  CH8 

HCX    XCCH3  -HCX    XC.CH8 


and  |             | 

HCV     /CC1  HCV     /CH 

XCX  X<r 

H  Cl 

ought  to  be  obtainable  from  the  xylene  of  formula  I. 

In  the  same  way  three  mono-substitution  products  should  be 
obtainable  from  the  xylene  of  formula  II.  The  method,  the 
principle  of  which  is  thus,  indicated  briefly,  while  theoretically 
simple  enough,  is  very  difficult  in  its  application,  except  in  the 
case  of  the  para  compounds.  Other  methods  have  therefore 
been  used,  and  these  will  be  discussed  under  mesitylene  and 
naphthalene.  It  may  be  said,  in  anticipation,  that  the  result 
of  all  observations  point  to  formula  I.  for  ortho-xylene,  to 
formula  II.  for  meta-xylene,  and  to  formula  III.  for  para- 
xylene. 

Ethyl-benzene,  C8H10(C6H5.C2H5).  —  This  hydrocarbon  is 
isomeric  with  the  xylenes,  but  differs  from  them  in  that  it  con- 
tains an  ethyl  group  in  the  place  of  one  hydrogen  of  benzene, 
instead  of  two  methyl  groups  in  the  place  of  two  hydrogens  of 
benzene.  It  is  made  by  treating  a  mixture  of  brom-benzene 
and  ethyl  bromide  with  sodium  :  — 

C6H5Br  +  C2H5Br  +  2  Na  =  C6H5  .  C2H5  +  2  NaBr. 

Its  conduct  toward  oxidizing  agents  distinguishes  it  from  the 
xylenes.  It  yields  benzoic  acid,  just  as  toluene  does.  In  this 
case,  as  in  that  of  toluene,  the  paraffin  radical  is  oxidized  to  car- 
boxyl.  It  has  been  found  that  no  matter  what  this  radical 


270       BENZENE  SERIES  OF  HYDROCARBONS 

is,   it   is   oxidized   to   carboxyl,   carbon    dioxide,   and   water. 
Thus,  the  conversions  indicated  below  take  place:  — 

C6H5.CH3  gives  C6H5.C02H. 

C6H5.C2H5  «  C6H5.C02H. 

C6H5.C3H7  «  C6H5.C02H. 

C6H5.C5Hn  «  C6H5.C02H. 


Mesitylene,  C9H12[C6H3(OH3)3].  —  Mesitylene  is  contained 
in  small  quantity  in  light  oil,  and  can  be  obtained  in  pure  con- 
dition from  this  source.  It  is  most  readily  prepared  by  treating 
acetone  with  sulphuric  acid  :  — 

3  C3H60  =  C9H12  +  3  H20. 

It  can  also  be  made  by  treating  methyl-acetylene,  CH3  .C  =  C  H, 
with  sulphuric  acid,  the  action  in  this  case  being  perfectly 
analogous  to  the  polymerization  of  acetylene  :  — 

3CH:CH  =  C6H6; 
3CH3.C!CH  =  C6H3(CH3)3. 

It  is  a  liquid  resembling  the  lower  members  of  the  series  in  its 
general  properties.     It  boils  at  163°. 

Its  conduct  towards  oxidizing  agents  shows  that  it  is  a  tri- 
methyl-benzene.  When  boiled  with  dilute  nitric  acid,  it  yields 
mesitylenic  acid,  C9H]002  and  uvitic  acid,  C9H804;  and,  by 
further  oxidation,  trimesitic  acid,  C9H6O6,  is  formed.  By  dis- 
tillation with  lime,  mesitylenic  acid  yields  meta-xylene  and 
carbon  dioxide  ;  uvitic  acid  yields  toluene  and  carbon  dioxide  ; 
and  trimesitic  acid  yields  benzene  and  carbon  dioxide.  The 
formation  and  decomposition  of  the  acids  may  be  represented 
by  the  equations  following  :  — 


MESITYLENE  273 

(CH3 

C6H3(CH3)3    +30  =  C6H3  J  CH3  +  H20  5 

Mesitylene  (  (^jj 

Mesitylenic  acid 

(  CH3  (  CH3 

C6H3  J  CH3     +30=  C6H3  ]  C02H  +  H20  ; 
(  C02H  (  C02H 

Mesitylenic  acid  Uvitic  acid 

(  CH3  r  C02H 

C6H3  J  C02H  +30  =  C6H3  ]  C02H  +  H20  ; 
(C02H  lC02H 

Uvitic  acid  Trimesitic  acid 


C6HJCH3  =C6H4 

(  CO  H  3 

V  ^U2«-  Meta-xylene 

Mesitylenic  acid 

(CH3 
C6H3  J  C02H  =  C6H5  .  CH3  +  2  C02  ; 

(  C02H  Toluene 

Uvitic  acid 

(C02H 

C6H3]C02H       •      =C6H6  +  3C02. 
(  C02H  Benzene 

Trimesitic  acid 

These  transformations  show  clearly  that  mesitylene  is  tri- 
raethyl-benzene,  but  they  do  not  show  in  what  relation  the 
methyl  groups  stand  to  each  other. 

An  ingenious  speculation  in  regard  to  this  relation  is  based 
upon  the  fact  that  mesitylene  is  formed  from  acetone.  It 
appears  probable  that  each  of  the  three  molecules  of  acetone 
taking  part  in  the  reaction, 


undergoes  the  same  change.  As  the  product  contains  three 
methyl  groups,  the  simplest  assumption  that  can  be  made  is 
that  each  acetone  molecule  gives  up  water  as  represented  thus:  — 


272       BENZENE  SERIES  OF  HYDROCARBONS 

CH3  -  CO  -  CH8  =  CH3  -  C  =  CH  +  H20. 

Acetone 

We  thus  have  three  molecules  of  methyl  acetylene, 
CH3  —  C  =  CH,  and  these  unite  to  form  trimethylbenzene. 
The  only  way  in  which  the  union  can  be  represented,  assuming 
that  all  three  act  in  the  same  way,  is  this  :  — 

CH3 
HC/ 


H3C  .  Cv      ^0  . 
H 

According  to  this  reasoning,  mesitylene  is  a  symmetrical  com- 
pound, —  that  is  to  say,  each  of  the  three  methyl  groups  bears 
the  same  relation  to  the  molecule  ;  and  the  same  is  true  of  each 
of  the  three  benzene-hydrogen  atoms. 

This  view  has  been  tested  by  replacing  the  three  hydrogen 
atoms  of  the  benzene  residue  successively  by  bromine  ;  and  it 
has  been  found  to  be  correct,  as  but  one  mono-bromine  substi- 
tution-product of  mesitylene  has  ever  been  obtained.  Accept- 
ing the  formula  above  given  for  mesitylene,  an  important 
conclusion  follows  regarding  the  structure  of  meta-xylene.  For 
we  have  seen  that,  by  oxidizing  mesitylene,  we  get,  as  the  first 
product,  mesitylenic  acid,  —  which  is  mesitylene,  one  of  whose 
methyls  has  been  converted  into  carboxyl.  As  all  the  methyl 
groups  bear  the  same  relation  to  the  molecule,  it  makes  no 
difference  which  one  is  oxidized.  The  acid  has  the  formula 

CH3 

HC/  \CH 

I  I 

C02H.Cv        ,C 

H 


PSEUDOCUMENE  273 

Now,  by  distilling  this  acid  with  lime,  carbon  dioxide  is  given 
off,  and  meta-xylene  is  produced. 

As  the  change  consists  in  removing  the  carboxyl,  and  re- 
placing it  by  hydrogen,  it  follows  that  meta-xylene  must  be 
represented  by  the  formula 

CH3 

HC/  \CH 

I  I 

H(X         ,C.CH3 
XX 
H 

and  consequently  that,  in  all  meta  compounds,  the  two  substi- 
tuting atoms  or  groups  bear  to  each  other  the  relation  which 
the  two  methyl  groups  bear  to  each  other  in  this  formula  for 
meta-xylene. 

• 

Pseudocumene,  C9H12[C6H3(CH3)3].  —  This  hydrocarbon, 
which  is  isomeric  with  mesitylene,  occurs  in  coal-tar  oil,  from 
which  it  can  be  prepared  in  pure  condition.  Its  properties  are 
similar  to  those  of  the  lower  members  of  the  series.  It  boils 
at  169.8°. 

Pseudocumene  has  been  made  synthetically  from  brorn-para- 
xylene  and  methyl  iodide,  and  also  from  brom-meta-xylene  and 
methyl  iodide.  How  this  is  possible,  will  be  understood  by  an 
examination  of  the  formulas  below  :  — 

CH3  CH3 

HC/  \CH  HC/  \CH 

II  II 

CBr  HC         yC.CH3 


CH  -^r 

Brom-para-xylene  Brom-meta-xylene 


274  BENZENE   SERIES    OF    HYDROCARBONS 

Replacing  the  bromine  by  methyl,  in  either  of  the  compounds 
represented,  the  product  would  have  the  formula 

CH3 

HC/ 

I 

HC\ 
\C/ 

CH3 

which  is  that  of  pseudocumene. 

Cymene, 

Para-methyl-isopropyl-benzene, 
This  hydrocarbon  is  of  special  importance,  on  account 
of  its  close  connection  with  two  well-known  groups  of 
natural  substances,  —  the  groups  of  which  camphor  and 
oil  of  turpentine  are  the  best-known  representatives.  It 
occurs  in  the  oil  of  caraway  and  the  oil  of  thyme.  The 
terpenes  are  hydrocarbons  of  the  formula  C10H16,  of  which 
oil  of  turpentine  is  the  best  known.  This  substance  easily 
gives  up  two  hydrogen  atoms  and  yields  cymene  when  heated 
with  iodine.  Cymene  is  best  prepared  by  treating  camphor 
with  phosphorus  pentasulphide,  zinc  chloride,  or  phosphorus 
pentoxide. 

It  is  a  liquid  of  a  pleasant  odor.     It  boils  at  175°. 

It  has  been  made  synthetically  from  para-brom-toluene  and 
isopropyl  bromide :  — 

PTT  PTT 

C6H4  <  £*•  +  C3H7Br  +  2  Na  =  C6H4  <  ^  +  2  NaBr, 

which  clearly  shows  its  relation  to  benzene.  As  the  final 
product  of  its  oxidation,  it  yields  para-phthalic  (terephthalic) 
acid :  — 

C6H4<^  gives  C6H4<^g; 
see  page  270. 


TETRAHYDROBENZENES  275 


Meta-cymene,  CCH4  <       ?  --  This  has  been  found  in  the 
O3±17 

products  of  distillation  of  rosin  (which  see). 

Tertiarybutyl-toluene,  G^<^Q^y  has  also  been 
found  in  the  products  of  distillation  of  rosin.  It  is  prepared 
on  the  large  scale  from  toluene  and  isobutyl  or  tertiarybutyl 
chloride  by  bringing  them  together  in  the  presence  of  alu- 
minium chloride  (see  pp.  265  and  363). 

HEXAHYDROBENZENES,  NAPHTHENES 

Caucasian  petroleum  consists  principally  of  a  mixture  of 
hydrocarbons  that  have  been  found  to  be  hydrogen  addition- 
products  of  members  of  the  benzene  series.  They  are  oils  that 
can  be  converted  into  members  of  the  benzene  series  by  passing 
them  through  tubes  heated  to  a  red  heat.  They  do  not  react 
with  concentrated  nitric  or  sulphuric  acid,  and  in  this  respect 
they  differ  markedly  from  the  benzene  hydrocarbons.  They 
are  called  naphthenes. 


CH 
Hexamethylene,  hexanaphthene,  CH2<  _,  _2'  ^    2>CH9. 


—  This  is  found  not  only  in  Caucasian  petroleum  but  in  the 
petroleum  from  other  sources.  American  petroleum  contains 
it  in  small  quantity.  It  can  be  made  artificially  by  reducing 


iodo-cyclohexane,  IHC<  ~2'       2>CH2.      It   is  formed  by 


reducing  benzene  with  hydrogen  in  the  presence  of  hot,  finely 
divided  nickel.  The  product  formed  when  benzene  is  treated 
with  concentrated  hydriodic  acid  is  methyl-pentamethylene, 

<CH2  .  CH2 
I      . 
CH2.CH2 

Other  hydrocarbons   of  this  series  are  hexahydrotoluene  or 

/"VET       OTT 

heptanaphthene,  CH3  .  CH  <       2  '  ~*  >  CH2,  hexahydroxylene 

v>x!2  .  vy-tlg 

or  octonaphthene,  (CH3)2C6H10,  etc. 


276  BENZENE   SERIES    OF    HYDROCARBONS 

TETRAHYDROBENZENES 

The  simplest  hydrocarbon  of  this  group  is  tetrahydrobenzene, 

CH2 .  CH2 .  CH 

|  ||     .     It  is  formed  from  brom-cyclohexane  by  elim- 

CH2.CH2.CH 
inating  hydrobromic  acid. 

Tetrahydrotoluene,  CH3 .  C6H8,  is  contained  in  the  essence 
of  resin. 

Hydrocarbons  CioH18.  —  There  are  several  hydrocarbons 
of  the  formula  C10H18  known  that  belong  to  the  series  of  tetra- 
hydrobenzenes.  The  principal  ones  are  related  to  the  terpenes 
(which  see). 

DlHYDROBENZENES 

A  number  of  the  members  of  this  group  have  been  made,  as, 
for  example,  dihydrobenzene,  C6H8,  dihydrotoluene,  C7H10,  di- 
hydroxylenes,  C8H12,  etc. 

Dihydro-o-xylene,  or  cantharene,  (CH3)2C6H6,  is  formed  by 
heating  cantharic  acid,  C10H1204,  with  lime. 


CHAPTER  XV 

DERIVATIVES  OF  THE  HYDROCARBONS, 
OF  THE  BENZENE  SERIES 

KECALLING  what  has  been  learned  under  the  head  of  De- 
rivatives of  the  Paraffins,  we  should  naturally  look  for  repre- 
sentatives of  all  the  classes  of  compounds  there  met  with. 
The  derivatives  of  the  paraffins  were  classified  as:  — 

1.  Halogen  derivatives. 

2.  Oxygen  derivatives,   including   the   Alcohols,   Aldehydes, 

Acids,  etc. 

3.  Sulphur  derivatives,  including  the  Mercaptans,  Sulphonio 

Acids,  etc. 

4.  Nitrogen    Derivatives,    including    Cyanides,   Amino    com- 

pounds, Nitro  compounds,  etc. 

5.  Metallic  derivatives. 

The  derivatives  of  the  benzene  hydrocarbons  may  be  classi- 
fied in  the  same  way,  but  a  change  in  the  order  of  treatment 
will  be  somewhat  more  convenient,  owing  to  many  points  of 
analogy  between  the  halogen  substitution-products,  the  nitro 
compounds,  and  the  sulphonic  acids.  All  these  three  classes 
of  derivatives  of  the  benzene  hydrocarbons  are  made  by  direct 
treatment  of  the  hydrocarbons  with  the  substituting  agents, 
and  in  some  respects  resemble  one  another,  so  that  they  will 
be  studied  in  connection.  As  the  amino  derivatives  of  this 
series  are  made  almost  exclusively  from  nitro  compounds  by 
reduction,  they  will  be  taken  up  in  connection  with  the  nitro 
compounds;  and,  further,  by  treatment  of  the  amino  com- 
pounds with  nitrous  acid,  a  new  class  of  nitrogen  derivatives, 

277 


278  DERIVATIVES    OF    THE   BENZENE   SERIES 

known  as  diazonium  and  diazo  compounds,  not  commonly  met 
with  in  connection  with  the  paraffins,  is  formed.  These  will 
be  taken  up  after  the  amino  compounds. 

After  these  classes  have  been  studied,  the  oxygen  derivatives, 
which  include  the  phenols  or  simple  hydroxyl  derivatives  of 
the  hydrocarbons,  the  alcohols,  aldehydes,  acids,  and  ketones 
will  be  taken  up  in  turn ;  and,  finally,  the  hydroxy-acids,  which 
are  strictly  analogous  to  the  hydroxy-acids  of  the  paraffin  series. 

There  are  thus  the  following  classes  :  — 

1.  Halogen  derivatives.          5.  Sulphonic          9.  Acids. 

2.  Nitro  compounds.  acids.  10.  Ketones  (and 

3.  Amino  compounds.  6.  Phenols.  Quinones). 

4.  Diazonium  and  Diazo       1.  Alcohols.          11.  Hydroxy-acids. 

compounds.  8.  Aldehydes. 

The  relations  of  most  of  these  classes  to  the  hydrocarbons 
are  the  same  as  those  of  the  corresponding  derivatives  of  the 
paraffin  series  to  the  paraffins  ;  and  the  general  methods  of 
preparation,  as  well  as  the  reactions,  are  the  same.  Hence, 
most  of  the  knowledge  acquired  in  the  first  part  of  the  course 
may  be  applied  to  the  series  now  under  consideration. 

An  enormous  number  of  derivatives  of  the  benzene  hydro- 
carbons have  been  prepared  and  studied,  but  only  very  few 
need  to  be  studied  in  order  to  make  the  chemistry  of  all  of 
them  clear.  In  the  following  a  few  of  the  more  important 
representatives  of  each  class  will  be  presented,  mainly  with 
the  object  of  illustrating  general  facts  and  general  relations. 

HALOGEN  DERIVATIVES  OF  BENZENE 

Very  little  need  be  said  in  regard  to  these  derivatives.  By 
direct  action  of  bromine  or  chlorine  upon  benzene  the  hydrogen 
atoms  are  replaced  one  after  another,  until,  as  the  final  products, 
hexa-chlor-benzene,  C6C16,  and  hexa-brom-benzene,  C6Br6,  are  ob- 
tained. When  the  action  takes  place  in  direct  sunlight, 
addition-products,  C6H6C16  and  C6H6Br6,  are  formed.  Benzene 


HALOGEN   DERIVATIVES   OF   BENZENE  279 

hexachloride,  C6H6C16,  is  formed  also  when  chlorine  is  con- 
ducted into  boiling  benzene.  The  addition-products  are  decom- 
posed, yielding  tri-substitution  products  of  benzene  and  halogen 
acid:  — 


The  substitution-products  are  very  stable.  They  are,  as  a 
rule,  formed  more  easily  than  the  halogen  derivatives  of  the 
paraffins,  and,  as  a  rule,  they  do  not  give  up  the  halogens  as 
readily.  Thus,  while  it  is  possible  in  the  paraffin  derivatives 
to  replace  chlorine  and  bromine  by  hydroxyl,  the  amino  group, 
etc.,  these  substitutions  cannot  easily  be  effected  in  the  benzene 
derivatives.  The  halogens  can  be  removed  by  sodium,  as 
shown  in  the  synthesis  of  hydrocarbons  :  — 

C6H5Br  +  CH3I  +  2  Na  =  C6H5  .  CH3  +  NaBr  +  Kal,  etc. 

They  can  also  be  removed  by  nascent  hydrogen,  the  hydrocar- 
bons being  regenerated  :  — 

C6H4C12  +  4  H  =  C6H6  +  2  HC1. 

This  kind  of  reverse  substitution  is  easily  effected  by  means  of 
alcohol  and  metallic  sodium. 

Chlor-benzene,  C6H5C1.  —  Chlor-benzene  can  be  made  by 
treating  benzene  with  chlorine,  but  the  action  is  slow.  The 
action  is  much  hastened  by  adding  a  little  iodine  or  iron  which 
act  as  carriers.  They  are  found  in  the  form  of  chlorides  at 
the  end  of  the  operation.  Chlor-benzene  can  also  be  made 
by  boiling  a  diazonium  salt  (which  see)  with  hydrochloric 
acid  :  — 

C6H5N2C1  +  HC1  =  C6H5C1  +  N2  +  HC1. 

Brom-benzene,  C6H5Br.  —  This  is  made  by  the  same  meth- 
ods as  those  used  in  making  chlor-benzene. 

When  brom-benzene  in  solution  in  ether  is  treated  with  mag- 
nesium powder,  it  forms  a  compound  of  the  formula  C6H5MgBr 


280  DERIVATIVES    OF   THE   BENZENE    SERIES 

(see   Barbier-Grignard   reaction,  p.  106).      This   reacts   with 
methyl  bromide  to  form  methyl-benzene  or  toluene,  thus  :  — 

C6H5MgBr  +  BrCH3  =  C6H5  .CH3  +  MgBr2. 

lodo-benzene,  C6H5I.  —  This  can  be  made  by  treating  ben- 
zene with  iodine  and  iodic  acid  :  — 

5  C6H6  +  4  I  +  HI03  =  5  C6H5I  +  3  H20  ; 

but  it  is  most  easily  made  through  the  diazonium  salt.     It  is  a 
liquid  that  solidifies  at  -  30°. 

Phenyliodoso  chloride,  C6H5IC12.  —  This  compound  is 
formed  when  iodo-benzene  in  chloroform  solution  is  treated  with 
chlorine.  When  it  is  treated  with  caustic  potash,  it  is  converted 
into  iodoso-benzene,  C6H5IO.  This  has  basic  properties,  and 
forms  salts  that  are  derived  from  the  hypothetical  base, 
C6H5I(OH)2,  as,  for  example,  C6H5I(O.CO.CH3)2. 

lodoxy-benzene,  C6H5IO2,  is  formed  from  iodoso-benzene, 
either  by  heating  it  alone  or  by  boiling  its  water  solution  :  — 


Diphenyliodonium  hydroxide,  (C6H5)2I.OH.  —  This  re- 
markable substance  is  formed  when  a  mixture  of  iodoso-  and 
iodoxy-benzene  is  shaken  with  silver  oxide  and  water  :  — 

C6H5IO  +  C6H5I02  +  AgOH  =  (C6H5)2  1.  OH  +  AgI03. 

It  is  strongly  alkaline  and  forms  salts  that  have  many  points 
of  resemblance  with  the  salts  of  thallium. 

Diphenyliodonium  hydroxide  may  be  regarded  as  the  di- 
phenyl  derivative  of  a  hypothetical  base,  iodonium  hydroxide, 
H2I(OH),  that  bears  to  iodine  a  relation  similar  to  that  which 
ammonium  hydroxide  bears  to  nitrogen.  Compounds  of  the 
same  order  are  known  in  which  sulphur  plays  the  same  part 
that  iodine  plays  in  the  iodonium  compounds,  and  nitrogen  in 
the  ammonium  compounds. 


HALOGEN   DERIVATIVES   OF   TOLUENE  281 

Dibrom-benzene,  C6H4Br2,  is  one  of  the  products  of  the  di- 
rect treatment  of  benzene  with  bromine  in  the  presence  of  a  car- 
rier. This  being  a  di-substitution  product  of  benzene,  it  follows, 
from  what  has  been  said  in  regard  to  isomerism  in  this  series 
of  hydrocarbons,  that  three  isomeric  varieties  of  the  substance 
ought  to  be  obtainable ;  and  the  interesting  question  suggests 
itself:  Which  one  of  the  three  possible  dibrom-benzenes  is  formed 
by  direct  treatment  of  benzene  with  bromine  ?  The  answer  to 
the  question  is  equally  interesting.  The  main  product  of  the 
action  is  para-dibrom-benzene,  while  there  is  always  formed  in 
much  smaller  quantity  some  of  the  ortho  product.  The  reason 
why  these  products  are  formed,  and  not  the  meta  compound,  is 
unknown ;  nor  has  any  plausible  hypothesis  been  suggested  to 
account  for  the  fact. 

In  studying  the  substitution-products  of  benzene,  one  of  the 
first  problems  that  presents  itself  i$  the  determination  of  the 
relations  which  the  substituting  atoms  or  groups  bear  to  each 
other.  The  determination  is  made,  as  has  been  stated,  by 
transforming  the  compounds  into  others,  the  relations  of  whose 
groups  are  known.  Thus,  to  illustrate,  when  benzene  is  treated 
under  the  proper  conditions  with  bromine,  two  dibroin-benzenes 
are  formed.  Without  investigation,  we,  of  course,  cannot  tell 
to  which  series  these  compounds  belong.  But,  by  treating 
that  product  which  is  formed  in  larger  quantity  with  methyl 
iodide  and  sodium,  we  get  para-xylene.  In  other  words,  by 
replacing  the  two  bromine  atoms  of  the  dibrom-benzene  by 
methyl  groups,  we  get  a  compound  which  we  know  belongs 
to  the  para  series ;  and,  therefore,  we  have  determined  that 
the  bromine  product  is  a  para  compound.  In  the  following  the 
chief  reactions  made  use  of  for  effecting  the  transformations 
of  the  derivatives  will  be  discussed. 

HALOGEN  DERIVATIVES  OF  TOLUENE 

As  toluene  is  made  up  of  a  residue  of  marsh  gas,  methyl, 
CH3,  and  a  residue  of  benzene,  phenyl,  C6H5,  it  yields  two 


282  -DERIVATIVES    OF   THE   BENZENE   SERIES 

classes  of  substitution-products:  (1)  Those  in  which  the  sub- 
stituting atom  or  group  replaces  one  or  more  hydrogen  atoms 
of  the  phenyl  group ;  and  (2)  those  in  which  the  substitution 
takes  place  in  the  methyl.  In  general,  when  treated  with 
chlorine  or  bromine  in  direct  sunlight,  or  at  the  boiling  tem- 
perature, toluene  yields  products  of  the  second  class';  while, 
when  treated  in  the  dark,  or  at  ordinary  temperatures,  in  the 
presence  of  iodine  or  some  other  carrier  (see  page  279),  it  yields 
products  of  the  first  class.  Thus,  we  have  the  two  parallel 
series  of  chlorine  derivatives :  — 

i  ii 

C6H4C1.CH3.  C6H5.CH2C1. 

C6H3C12.CH3.  C6H5.CHGl2. 

C6H2C13.CH3.  C6H5.CC13. 

When  a  member  of  the  fjjst  class  is  oxidized,  the  methyl  is 
changed,  and  the  rest  of  the  compound  remains  unchanged, 
as  in  the  case  of  toluene.  Thus,  the  first  substance  of  class  I. 
yields  the  product  C6H4C1.C02H;  the  second,  C6H3C12.C02H, 
etc.  These  products  are  substituted  benzoic  acids.  On  the 
other  hand,  all  the  members  of  the  second  class  yield  the  same 
product  that  toluene  does ;  viz.,  benzoic  acid.  Hence,  by  treat- 
ment with  oxidizing  agents,  it  is  easy  to  distinguish  between 
the  members  of  the  two  classes.  Further,  the  halogen  atoms 
contained  in  the  methyl  react  like  the  halogen  atoms  in  paraffin 
derivatives,  while  those  in  the  benzene  ring  do  not.  When,  for 
example,  the  compound  C6H5.CHC12,  which  is  called  benzal 
chloride,  is  superheated  with  water,  both  chlorine  atoms  are 
replaced  by  oxygen,  the  product  being  the  aldehyde  C6H5.CHO, 
which,  as  we  shall  see,  is  the  familiar  substance,  oil  of  bit- 
ter almonds.  When,  however,  the  isoineric  di-chlor-toluene, 
C6H3C12.CH3,  is  superheated  with  water,  no  change  takes 
place. 

Regarding  those  simple  substitution-products  of  toluene 
which  contain  one  halogen  atom  in  the  phenyl,  such  as  mono- 


NITEO   COMPOUNDS   OF   BENZENE   AND   TOLUENE     283 

brom-toluene,  C6H4Br.CH3,  we  see  that  they  are  di-substi- 
tution  products  of  benzene,  and  hence  capable  of  existing  in 
three  isomeric  varieties,  ortho,  meta,  and  para.  The  prod- 
ucts formed  by  direct  treatment  of  toluene  with  chlorine  or 
bromine  are  mixtures  of  the  para  and  the  ortho  com- 
pounds. 

The  determination  of  the  series  to  which  one  of  these  products 
belongs  can  be  made  by  replacing  the  halogen  by  methyl,  and 
thus  getting  the  corresponding  xylene.  The  main  product  of 
the  action  of  bromine  on  toluene  is  in  this  way  converted  into 
para-xylene,  and  is  therefore  para-brom-toluene. 

HALOGEN  DERIVATIVES  OF  THE  HIGHER  MEMBERS  OF 
THE  BENZENE  SERIES 

Concerning  the  halogen  derivatives  of  xylene,  it  need  only  be 
said  that  the  only  one  of  the  three  xylenes  from  which  pure 
products  can  easily  be  obtained  is  para-xylene.  When  this  is 
treated  with  bromine,  it  yields  but  one  mono-brom-xylene.  The 
significance  of  this  fact  has  been  discussed  above.  The  mono- 
substitution  products  obtained  from  the  other  xylenes  are 
mixtures  which  it  is  very  difficult,  and  in  some  cases  impos- 
sible, to  separate  into  their  constituents.  Mesitylene  and 
pseudocumene,  though  both  are  tri-m ethyl-benzenes,  conduct 
themselves  quite  differently  towards  bromine, —  the  former 
yielding  only  one  mono-bromine  product ;  the  latter,  a  mixture 
of  several. 

NITRO  COMPOUNDS  OF  BENZENE  AND  TOLUENE 

In  treating  of  nitro  compounds  in  connection  with  the  paraf- 
fin derivatives  (see  p.  101 ),  it  was  stated  that  they  are  obtained 
much  more  readily  from  the  benzene  hydrocarbons  than  from 
the  paraffins.  Only  a  few  nitro  derivatives  of  the  paraffins  are 
known.  As  will  be  remembered,  they  cannot  be  prepared  by 
treating  the  paraffins  with  nitric  acid,  but  must  be  made  by 


284  DERIVATIVES   OF   THE   BENZENE   SERIES 

circuitous  methods,  the  principal  one  being  the  treatment  of 
the  halogen  derivatives  with  silver  nitrite  :  — 

C2H6Br  +  AgN02  =  C2H5(N02)  +  AgBr. 

Nitro-ethane 

The  preparation  of  a  nitro  derivative  of  a  hydrocarbon  of 
the  benzene  series  is  a  simple  matter.  It  is  only  necessary  to 
bring  the  hydrocarbon  in  contact  with  strong  nitric  acid,  when 
reaction  takes  place,  and  one  or  more  hydrogen  atoms  of  the 
hydrocarbon  are  replaced  by  the  nitro  group  N02,  as  repre- 
sented in  the  equations  :  — 


C6H6  -f  HNO,  =  C6H5  .  N02        +  H20  ; 

C«H5.N02    +  HN03  =  C«H4(N02)2      +  H20; 


C6H4  <  3        e3 

The  nitro  compounds  thus  obtained  are  not  acids,  nor  are 
they  esters  of  nitrous  acid.  If  they  were  esters  of  nitrous 
acid,  they  would  be  saponified  by  caustic  alkalies,  yielding  a 
nitrite  and  hydroxyl  derivative  similar  to  the  alcohols.  They 
do  not  act  in  this  way.  When  treated  with  nascent  hydrogen, 
they  are  reduced  to  amino  compounds  or  substituted  ammonias. 
Thus,  nitro-benzene,  C6H5.N02,  gives  aniline  or  ainino-berizene, 
C6H5  .  NH2,  which  is  a  substituted  ammonia  similar  to  methyl  - 
amine  and  ethyl-amine.  As  in  these  the  radical  is  in  com- 
bination with  nitrogen,  it  is  probable  that  the  radical  is  in 
combination  with  nitrogen  in  the  nitro  compounds  also,  as 
shown  in  the  formula,  C6H5  .  N02.  Everything  known  about 
these  nitro  compounds  is  in  harmony  with  this  view.  The 
formation  of  a  nitro  compound  by  the  action  of  nitric  acid  on 
a  hydrocarbon  is  represented  thus  :  — 


C6H6H  +  HO  .  N02  =  C6H5  .  N02  +  H20. 


DINITRO-BENZENE  285 

Mono-nitro-benzene,  C6H5 .  NO2.  —  This  substance  is  made 
by  treating  benzene  with  fuming  nitric  acid,  or  with  a  mixture 
of  ordinary  concentrated  nitric  and  sulphuric  acids.  In  the 
latter  case,  the  sulphuric  acid  facilitates  the  reaction,  probably 
by  preventing  the  dilution  of  the  nitric  acid  by  the  water 
necessarily  formed. 

Experiment  57.  Make  a  mixture  of  75CC  ordinary  concentrated 
sulphuric  acid,  and  75CC  ordinary  concentrated  nitric  acid.  Let  it  cool  to 
the  room  temperature.  Put  the  vessel  containing  it  in  water,  and  add 
about  15CC  to  20CC  benzene,  a  few  drops  at  a  time,  waiting  each  time  until 
the  reaction  is  complete.  Shake  well  until  the  benzene  is  dissolved,  heat 
to  60°  for  an  hour  on  a  water-bath,  then  pour  slowly  into  about  a  litre  of 
cold  water.  A  yellow  oil  will  sink  to  the  bottom.  This  is  nitro-benzene. 
Pour  off  the  acid  and  water  ;  wash  two  or  three  times  with  water  ;  sepa- 
rate the  water  by  means  of  a  pipette,  and  dry  by  adding  a  little  granulated 
calcium  chloride.  After  standing  for  some  time,  pour  off  from  the  calcium 
chloride,  and  distil,  noting  the  boiling  temperature. 

Nitro-benzene  is  a  liquid  that  boils  at  209°,  melts  at  6°,  and 
has  the  specific  gravity  1.2.  Its  odor  is  like  that  of  the  oil  of 
bitter  almonds,  and  it  is  hence  used  to  some  •  extent  instead  of 
the  latter.  It  is  known  as  the  essence  ofmirbane.  It  is  manu- 
factured on  the  large  scale,  and  used  principally  in  the  prepa- 
ration of  aniline.  Its  vapor  is  poisonous. 

Dinitro-benzene,  C6H4(NO2)2 This  is  a  product  of  the 

further  action  of  nitric  acid  on  benzene,  or  on  nitro-benzene. 

Experiment  58.  Make  a  mixture  of  50CC  concentrated  sulphuric 
acid,  and  50CC  fuming  nitric  acid.  Without  cooling  add  very  slowly  about 
10CC  benzene  from  a  pipette  with  a  fine  opening.  After  the  action  is 
over,  boil  the  mixture  for  a  short  time;  then  pour  into  about  half  a  litre 
of  water.  Filter  off  the  solid  substance  thus  precipitated,  press  it  between 
layers  of  filter-paper,  and  crystallize  from  alcohol. 

Dinitro-benzene  crystallizes  in  long,  fine  needles,  or"  thin, 
rhombic  plates.  Melting-point,  90°. 

By  means  of  two  reactions,  which  will  be  described  under 
the  head  of  Diazo  Compounds,  it  is  a  simple  matter  to  replace 


286  DERIVATIVES    OF   THE   BENZENE   SERIES 

the  two  nitro  groups  by  bromine,  thus  converting  dinitro-ben- 
zene  into  dibrom-benzene.  When  the  latter  is  converted  into 
xylene,  the  product  is  nieta-xylene.  Hence,  ordinary  dinitro- 
benzene  is  a  meta  compound. 

Nitro-toluenes,  C6H4(NO2)  .  CH3. — When  toluene  is  treated 
with  nitric  acid,  substitution  always  takes  place  in  the  phenyl. 
Over  56  per  cent  of  the  ortho  product  is  formed,  about  40  per 
cent  of  the  para,  and  about  4,  per  cent  of  the  meta.  The 
higher  the  temperature,  the  larger  the  proportion  of  the  ortho 
product  formed. 

By  treatment  with  nascent  hydrogen,  the  nitro-toluenes  are 
converted  into  the  corresponding  amino  compounds,  called 
Toluidines  (which  see). 

Trinitro-toluene,  C6H2(NO2)3  .  CHa,  is  now  used  exten- 
sively as  an  explosive. 

f^TT 

Trinitro-tertiarybutyl-toluene,  CeHCNOz^^Qjj3^,  has 
the  odor  of  musk  and  is  known  as  "  artificial  musk." 

AMINO  COMPOUNDS  OF  BENZENE,  ETC. 

The  amino  derivatives  of  the  paraffins  are  made,  for  the  most 
part,  by  treating  the  halogen  derivatives  with  ammonia  (see  p.  96). 
In  treating  of  these  derivatives,  however,  attention  was  called  to 
the  fact  that  they  can  also  be  made  by  treating  nitro  compounds 
with  nascent  hydrogen  (see  p.  99).  The  latter  method  is  one  of 
great  importance  in  the  benzene  series.  It  is  used  exclusively 
in  the  preparation  of  the  amino  derivatives  of  the  benzene 
hydrocarbons.  Several  of  these  derivatives  are  well  known, 
the  simplest  and  best  known  being  ammo-benzene  or  aniline. 

Aniline,  C6H7N(CbH5.NH2).  —  Aniline  was  first  obtained 
from  indigo  by  distillation.  Anil  is  the  Portuguese  and  French 
name  of  the  indigo  plant,  and  it  is  from  this  that  the  name 
aniline  is  derived.  Aniline  is  found  in  coal  tar  and  in  bone  oil, 


ANILINE  287 

a  product  of  the  distillation  of  bones.  It  is  prepared  by  re- 
ducing nitro-benzene  with  nascent  hydrogen.  On  the  large 
scale  the  hydrogen  is  obtained  from  hydrochloric  acid,  iron,  and 
water.  Only  a  small  quantity  of  acid  is  required.  After  the 
reaction  has  started,  the  iron  acts  upon  the  water  in  the  presence 
of  ferrous  chloride,  yielding  hydrogen  and  ferric  hydroxide  :  — 

C6H5N02  +  2  Fe  +  4  H20  =  C6H5NH2  +  2  Fe(OH)3. 

For  laboratory  purposes  tin  and  hydrochloric  acid  are  perhaps 
best.  Other  reducing  agents,  such  as  an  ammoniacal  solution 
of  ammonium  sulphide,  hydriodic  acid,  etc.,  also  effect  the 
change,  which  is  represented  by  the  following  equation  :  — 

C6H5  .  N02  +  6  H  =  C6H5  .  NH2  +  2  H20. 


Experiment  59.  Arrange  a  litre  flask  with  a  stopper  and  a  straight 
glass  tube  from  two,  to  three  feet  long.  Put  in  the  flask  90s  granulated 
tin  and  50&  nitro-benzene.  Now  add  gradually  20Qg  ordinary  concentrated 
hydrochloric  acid.  Heat  on  the  water-bath  until  all  the  tin  is  dissolved, 
then  add  some  water  and  sodium  hydroxide  until  the  precipitate  first 
formed  is  nearly  all  dissolved.  Distil  in  steam.  Separate  by  means  of  a 
separating  funnel. 

Aniline  is  a  colorless  liquid  that  soon  becomes  colored  in 
the  air.  It  boils  at  182.5°.  It  solidifies  at  a  low  temperature 
and  melts  at  —  8°  ;  it  is  easily  soluble  in  alcohol,  but  slightly 
soluble  in  water.  The  solution  in  water  has  only  a  slight  alka- 
line reaction.  Aniline  is  poisonous.  Its  salts  with  strong 
acids  have  an  acid  reaction. 

Experiment  60.  To  an  aqueous  solution  of  a  little  of  the  aniline 
obtained  in  Exp.  59,  in  a  test-tube,  add  a  filtered  solution  of  bleaching 
powder  (calcium  hypochlorite).  A  beautiful  violet  color  is  produced. 

To  a  solution  of  aniline  in  concentrated  sulphuric  acid  add  a  small 
grain  of  potassium  bichromate.  A  blue  color  is  produced. 

Aniline  bears  to  benzene  the  same  relation  that  ethyl-amine 
or  amino-ethane  bears  to  ethane.  It  is  a  substituted  ammonia, 
and,  like  other  bodies  of  the  same  class,  it  unites  directly  with 


288  DERIVATIVES    OF    THE   BENZENE    SERIES 

acids,  forming  salts.     Thus,  with  hydrochloric,  nitric,  and  sul- 
phuric acids  the  action  takes  place  as  represented  below :  — 

C6H5.NH2  +  HC1     =  (C6H5.NH3)C1 ; 
C6H5 .  NH2  +  HN03  =  (C6H5 .  NH3)N03 ; 
C6H5 .  NH2  +  H2S04  =  C6H5 .  NH3HS04. 

The  hydrochloride  is  known  in  the  trade  as  aniline  salt. 

The  decomposition  of  aniline  hydrochloride  by  means  of 
a  caustic  alkali  takes  place  as  represented  in  the  following 
equation :  — 

C6H5 .  NH8C1  +  KOH  =  C6H5 .  NH2  +  H20  +  KC1. 

Derivatives  of  Aniline.  —  Aniline  is  much  more  sensitive 
to  the  action  of  reagents  then  benzene  or  its  halogen  or  nitro 
derivatives.  Substitution  takes  place  easily,  but  there  is  danger 
that  the  aniline  will  be  decomposed  by  the  substituting  agent. 
Among  the  substitution-products  that  find  extensive  applica- 
tion is  one  of  the  sulphonic  acids. 

Dimethyl-aniline,  C6H5N(CH3)2. — When  aniline  is  treated 
with  methyl  bromide  and  similar  halogen  derivatives  of  the 
paraffins,  residues  of  the  paraffins  are  introduced  into  the 
aniline  in  place  of  the  ammonia  hydrogen  atoms  :  — 

C6H5.  NH2  +  CH3Br  =  (C6H5.  NHCH3) .  HBr ; 
C6H5 .  NH2  +  2  CH3Br  =  [C6H5 .  N(CH3)2] .  HBr  +  HBr. 

Of  the  compounds  obtainable  by  this  method,  dimethyl-aniline 
is  the  most  important  from  the  technical  point  of  view.  It  is 
prepared  by  a  modification  of  the  above  method  —  by  heating 
aniline  with  hydrochloric  or  sulphuric  acid  and  methyl  alcohol 
in  a  closed  vessel :  — 

C6H5 .  NH2.  HC1  +  CH3OH  =  C6H5 .  NH2  +  CH3C1  +  H20 ; 

C6H5 .  NH2  +  CH3C1  =  C6H5 .  NH(CH3) .  HC1 ; 
C6H5.NH(CH3).HC1  4-  CH3OH  =  C6H5.N(CH3)2.HC1  +  H20. 

It  is  a  liquid  that  boils  at  192°,  and  solidifies  at  0.5°. 


TOLUIDINES  289 

Diphenylamine,  (C6H5)2NH.  —  This  is  formed  from  aniline 
by  the  introduction  of  a  phenyl  group,  C6H5,  for  one  of  the 
ammonia  hydrogen  atoms.  It  is  prepared  on  the  large  scale, 
and  finds  extensive  use  in  the  manufacture  of  dyes  and  as  an 
addition  to  explosives  for  the  purpose  of  increasing  their  sta- 
bility. It  is  made  by  heating  aniline  with  aniline  hydrochlo- 
rideat200°:  — 


It  is  a  solid  that  crystallizes  in  white  laminae  from  ligroin. 
It  melts  at  54°  and  boils  at  302°..  It  forms  salts  with  strong 
acids,  but  these  are  decomposed  by  water. 

Acetanilide,  C6H5  .  NH  .  COCH3.  —  Aniline  reacts  with  acid 
chlorides  as  ammonia  does.  While  ammonia  forms  amides, 
aniline  forms  anilides.  Thus,  with  acetyl  chloride,  ammonia 
gives  acetamide,  and  aniline  gives  acetanilide  :  — 

CH3.COC1  +  NH3  =  CH3.COim2  +  HC1  ; 

2.C6H5=CH3.CO.NH.C6H54-HC1. 


Acetanilide  is  more  easily  prepared  by  boiling  aniline  with 
glacial  acetic  acid  for  24  hours  :  — 


Acetanilide  crystallizes  from  water  in  large,  colorless  plates. 
It  melts  at  115°  and  boils  at  304°.  It  is  used  in  medicine 
under  the  name  antifebrine. 


Toluidines,  amino-toluenes,  C6H4<        2<  —The  toluidines, 

L»±±3 

of  which  there  are  three  corresponding  to  the  three  nitro- 
toluenes,  are  made  from  the  latter  in  the  same  way  that  aniline 
is  made  from  nitro-benzene.  Ortho-  and  para-toluidine  are  used 
extensively  in  the  industries. 

The   properties  of  the  toluidines  are  much   like  those   of 
aniline. 


290  DERIVATIVES   OF   THE  BENZENE   SERIES 

Treated  with  various  oxidizing  agents,  a  mixture  of  aniline 
and  the  toluidines  is  converted  into  a  compound  known  as 
rosaniline.  This  is  the  mother  substance  of  the  large  group 
of  compounds  known  as  the  aniline  dyes.  Rosaniline  and  its 
derivatives,  the  aniline  dyes,  will  be  treated  of  under  Tri-phenyl- 
methane  (which  see). 

Nitrous  acid  converts  the  salts  of  the  toluidines  into  diazo- 
nium  compounds  analogous  to  those  formed  from  aniline  salts 
(see  Diazo  Compounds). 

The  xylidines  bear  to  the  three  xylenes  the  same  relation 
that  aniline  bears  to  benzene.  It  is  not  a  simple  matter  to  get 
any  one  of  them  in  pure  condition. 

DIAZONIUM  COMPOUNDS  OF  BENZENE 

The  usual  action  of  nitrous  acid  on  amino  compounds  is 
represented  by  the  equation,  — 

K.NH2  +  HN02  =  R.OH  +  H20  +  N2. 

When  an  amino  derivative  of  a  hydrocarbon  of  the  benzene 
series  is  treated  with  nitrous  acid  at  low  temperatures,  a  prod- 
uct is  obtained  which  contains  two  nitrogen  atoms,  and  which 
is,  therefore,  called  a  diazo  compound.  Thus,  in  the  case  of 
aniline  sulphate,  the  action  is  represented  by  the  equation,  — 


C6H5NH2.  H2S04  +  HN02  =  C6H5N2.  HS04  +  2  H20. 

Aniline  sulphate  Benzene-diazonium  sulphate 

So,  also,  with  the  nitrate  we  have,  — 

C6H5NH2.  HN03  +  HN02  =  C6H5K2.  N03  +  2  H20. 

Aniline  nitrate  Benzene-diazonium  nitrate 

The  salts  thus  formed  are  called  diazonium  salts  for  reasons 
which  will  presently  be  stated.  The  method  here  given  for 
the  preparation  of  benzene-diazonium  nitrate  is  not  the  one  used 
by  the  discoverer.  He  passed  nitrogen  trioxide  into  an  emul- 
sion of  the  amino  compound  in  alcohol.  If  a  solution  of  the 
diazonium  salt  is  wanted,  which  is  generally  the  case,  the  cal- 


DIAZONITJM   COMPOUNDS    OF   BENZENE  291 

Ciliated  quantity  of  sodium  nitrite  is  added  in  water  solution 
and  then  the  calculated  quantity  of  hydrochloric  acid  to  de- 
compose the  sodium  nitrite.  Thus  action  is  secured  between 
the  aniline  salt  and  the  nitrous  acid  as  it  is  set  free.  If  the 
dry  diazonium  salt  is  wanted,  the  salt  to  be  diazotized  may  be 
suspended  in  glacial  acetic  acid  or  absolute  alcohol  and  amyl 
nitrite  slowly  added.  Here  too  the  nitrous  acid  acts  as  it  is 
set  free  from  the  amyl  nitrite.  For  the  purposes  of  study  the 
sulphate  may  be  used. 

Experiment  61.  Dissolve  15=  aniline  in  9-10  times  this  weight  of  ab- 
solute alcohol  (in  any  case  this  should  not  be  of  less  strength  than  95  per 
cent) ;  add  slowly  20s  concentrated  sulphuric  acid.  A  thick  paste  of  aniline 
sulphate  separates  at  first,  but  on  further  and  somewhat  more  rapid  addi- 
tion of  the  rest  of  the  sulphuric  acid  the  precipitate  first  formed  passes  again 
into  solution.  The  solution  thus  obtained  is  allowed  to  cool  down  at  least 
to  the  temperature  of  the  room,  but  it  should  not  be  cooled  so  low  as  to 
cause  a  separation  of  aniline  sulphate.  Now  add  20?  amyl  nitrite,  which 
is  a  little  more  than  the  calculated  quantity.  During  the  process  the  tem- 
perature rises  only  slightly,  and  even  this  can  be  prevented  by  cooling  the 
vessel  in  water.  In  10-15  minutes  the  benzene-diazonium  sulphate  separates 
in  beautiful  needles,  and  the  whole  mass  solidifies,  forming  a  crystalline 
paste.  Filter  with  the  aid  of  a  pump  and  wash  with  a  little  alcohol  and 
ether.  If,  after  the  addition  of  the  amyl  nitrite,  the  crystalline  paste  is 
not  formed  in  about  15  minutes,  add  a  few  drops  of  ether.  The  reaction 
involved  is  represented  by  the  following  equation  :  — 

C6H6N.S04H  +  C5HnN03  =  C6H5N.S04H  +  C5HUOH  +  H20. 
II!  Ill 

H3  N 

Aniline  acid  sulphate      Amyl        Benzene-diazonium        Amyl 
nitrite  sulphate  alcohol 

With  the  benzene-diazonium  sulphate  thus  obtained  perform  the  ex- 
periments described  below. 

(a)  Dissolve  a  little  of  the  salt  in  water  at  the  ordinary  temperature, 
and  allow  the  solution  to  stand.  Decomposition,  indicated  by  change  of 
color,  and  a  marked  change  in  odor  will  take  place. 

(6)  Boil  a  little  with  water  in  a  test-tube,  and  notice  the  odor  of 
phenol  or  carbolic  acid. 


292  DERIVATIVES    OF   THE   BENZENE    SERIES 

(c)  Boil  a  few  grams  with  alcohol  in  a  test-tube,  and  notice  the  ease 
•with  which  the  decomposition  takes  place.     The  chief  product  is  ethyl- 
phenyl  ether  or  phenetol,  C^R^.O.  C^B. 

(d)  Boil  some  with  concentrated  hydrochloric  acid.     Chlor-benzene  is 
formed,  which  sinks  to  the  bottom  when  water  is  added. 

In  all  these  experiments  a  gas  is  evolved  which  can  be  shown  to  be 
nitrogen.  Collect  some,  and  show  that  it  does  not  support  combustion. 

(e)  Heat  a  very  little  of  the  compound,  dried  by  pressing  in  filter- 
paper,  on  platinum  foil  and  note  the  detonation. 

The  above  experiments  serve  to  indicate  the  instability  of 
benzene-diazonium  sulphate.  This  same  instability  is  charac- 
teristic of  all  diazonium  salts,  and  it  is  the  ease  with  which 
they  undergo  a  variety  of  changes  that  makes  them  so  valu- 
able. The  principal  changes  are  :  — 

1.  That  illustrated  in  Exp.  61  (6),  which  is  brought  about 
by  boiling  with  water.     The  action  is  represented  thus :  — 

C6H5N2.S04H  +  H20  =  C6H5.OH  +  N2  +  H2S04. 

•      Phenol 

2.  That  illustrated  in  Exp.  61  (c),  which  is  effected  by  boil- 
ing with  alcohol :  — 

C6H5N2.S04H  +  C2H5.OH  =  C6H5.O.C2H5  +  N2  +  H2S04. 

Phenetol 

In  some  cases  alcohol  reacts  in  another  way,  thus  :  — 
EN2C1  +  C2H5OH  =  RH  +  N2  +  C2H40  +  HC1. 

The  result  of  this  is  the  substitution  of  hydrogen  for  the 
diazo  group.  Sometimes  both  reactions  take  place  with  alcohol. 

3.  That  effected  by  hydrochloric  acid  as  illustrated  in  Exp. 
61  (d):- 

C^H.^, .  N03  +  HC1  =  C6H5C1  +  N2 + HNOS. 

Mono-chlor-benzene 

This  reaction  is  much  facilitated  by  the  addition  of  cuprous 
chloride  (Sandmeyer's  reaction). 


CONSTITUTION    OF   THE   DIAZONIUM   SALTS  293 

Benzene-diazonium  chloride  reacts  with  potassium  iodide  as 
shown  in  the  equation  :  — 

C6H5N2C1  +  KI  =  C6H6I  +  KC1  +  N2. 

Changes  similar  to  the  last  are  effected  by  hydrobromic  and 
hydriodic  acids,  the  chief  products  being  brom-benzene  and 
iodo-benzene  respectively.  Here  also  the  corresponding  cuprous 
salts  are  of  great  assistance. 

From  the  above  it  follows  that,  if  we  have  a  compound  con- 
taining a  nitro  group,  we  can,  by  making  the  diazonium  salt, 
transform  it  (1)  into  the  corresponding  hydroxyl  derivative  j 
(2)  into  the  corresponding  chlorine,  bromine,  or  iodine  deriva- 
tive; or  (3)  we  can  make  ethers  containing  such  groups  as 
C2H50,  CH30,  etc.  These  reactions  involving  the  use  of  the 
diazonium  salts  have  been  used  very  extensively  in  the  inves- 
tigation of  the  substitution-products  pf  the  benzene  series. 

NOTE  FOR  STUDENT.  —  How  can  the  relation  of  the  groups  in  dinitro- 
benzene  be  determined  by  using  the  diazonium  reactions  ? 

Constitution  of  the  Diazonium  Salts.  —  The  salts 
formed  by  the  action  of  nitrous  acid  on  aniline  salts  are 
salts  of  a  strong  base  which  are  to  be  compared  with  the  alkali 
salts.  It  has  been  shown  by  determinations  of  the  freezing 
point  and  of  the  electrical  conductivity  of  the  solutions  of 
these  salts  in  water  that  they  are  broken  down  into  ions  in  the 
same  way  as  salts  of  strong  bases.  This  suggests  that  they 
are  analogous  to  ammonium  salts,  and  the  view  that  is  most 
in  accordance  with  all  the  facts  is  that  represented  by  such 
formulas  as  the  following:  — 


C6H5  .  N  -  Cl  ;         C6H5  .  N  -  N03  ;         C6H5  -  N  -  HS04. 
Ill  HI  111 


As  the  salts  are  analogous  to  ammonium  salts,  they  are  called 
diazonium  salts.     According  to  this  view  they  are  to  be  regarded 


DERIVATIVES    OF   THE   BENZENE   SERIES 

as  aniline  salts  into  which  a  nitrogen  atom  has  been  introduced 
in  place  of  three  hydrogen  atoms :  — 

C6H5  -  N  -  01      — »-     C6H6  -  N  -  01; 

HI  III 

H3  N 

C6H5-N-N08    — >-    C^-N-NOs. 

Ill  111 

H3  N 

Metallic  Derivatives  of  Diazo-benzene  and  of  Isodiazo- 
benzene.  —  When  a.diazonium  salt  is  treated  in  the  cold  with 
caustic  potash  a  potassium  salt  of  the  formula  C6H5 .  N2 .  OK  is 
formed.  When  this  is  treated  with  ethyl  iodide  it  gives  an 
ether  of  diazo-benzene,  C6H5 .  ]ST2 .  OC2H5.  The  fact  that  the 
ethyl  in  this  compound  is  in  combination  with  oxygen  is  shown 
by  the  character  of  the  products  formed  when  it  is  decomposed. 
It  does  not  yield  ethylamine  as  it  would  if  the  ethyl  were  in 
combination  with  nitrogen.  When  the  above-mentioned  potas- 
sium salt  is  treated  with  phenols  (which  see),  it  reacts  with 
them  at  once,  forming  azo  compounds  (which  see). 

When  the  ordinary  potassium  salt  of  diazo-benzene  is  heated 
with  concentrated  caustic  potash  at  130°,  it  is  converted 
into  the  isomeric  compound,  potassium  iso-diazo-benzene  oxide, 
by  molecular  rearrangement.  This  does  not  easily  give  azo 
compounds  with  phenols.  With  ethyl  iodide  it  gives  a  com- 
pound in  which  the  ethyl  is  in  combination  with  nitrogen.  It 

P  TT 
is  a  nitroso  compound  of  the  formula  C6H5.N  <    a    5. 

The  facts  above  stated  suggest  that  the  ordinary  or,  normal 
potassium  diazo-benzene  oxide  has  the  structure  represented  by 
the  formula  C6H5  —  1ST2  —  OK,  that  the  isomeric  compound  has 
the  formula  C6H5  —  NK.NO,  and  that  they  are  derived  from 
the  two  compounds  :  — 

C6H5 .  N2 .  OH ;  C6H6 .  NH .  NO. 

Diazo-benzene  hydroxide  Phenyl  nitrosamine 


DIAZO-AMINO   COMPOUNDS  295 

It  has  been  suggested  that  the  two  potassium  salts  and 
other  similar  salts  are  stereoisorneric,  as  represented  in  the 
formulas :  — 

C6H5  -  N  C6H5  -  N 

II  1! 

KO.N  N. OK 

Normal  potassium-diazo-benzene  oxide  Potassium  iso-diazo-benzene  oxide 

By  way  of  explanation  of  these  formulas,  it  should  be  said 
that  they  involve  the  conception  that  the  nitrogen  atom  exerts 
its  affinities  in  the  direction  of  three  edges  of  a  tetrahedron, 
thus : — 


When  combined  with  another  nitrogen  atom  by  double  union 
the  figures  representing  this  condition  would  be :  — 


or 


There  are  two  ways  in  which  the  groups  or  atoms  X  and  Y 
can  be  arranged  in  space,  or  there  should  be  two  isomeric  forms 
of  compounds  containing  a  group  of  two  nitrogen  atoms  of  the 
form  -N  =  N-. 

Further  evidence  is  necessary  to  determine  which  of  the  two 
views  presented  is  correct. 

Diazo-amino  Compounds.  — When  a  diazonium  salt  reacts 
with  an  amino  compound  a  diazo-amino  compound  is  formed, 


296  DERIVATIVES    OF   THE   BENZENE   SERIES 

as,  for  example,  when  benzene-diazonium  chloride  acts  upon 
aniline :  — 

C6H5 .  N2C1  +  NH2 .  C6H5  =  C6H5N2 .  NH .  C6H5  +  HC1. 

As  will  be  seen,  the  residue  of  the  diazonium  salt  takes  the  place 
of  one  of  the  hydrogen  atoms  of  the  amino  group.  Diazo-amino- 
benzene  forms  golden  yellow  laminae  or  prisms.  It  is  insoluble 
in  water,  but  readily  in  hot  alcohol.  When  heated  with  aniline 
hydrochloride  it  is  transformed  into  amino-azo-benzene  :  — 
C6H5 .  N2 .  NH .  C6H5  — >-  C6H5 .  N2 .  C6H4 .  NH2. 

Other  diazo-amino  compounds  act  in  the  same  way.  The 
product  formed  in  the  above  case  is  an  amino  derivative  of 
a  compound,  C6H5 .  N2 .  C6H5,  known  as  azo-benzene. 

Azo-benzene,  C6H5 .  N2 .  C6H5,  is  formed  by  partial  reduc- 
tion of  nitro-benzene  in  alkaline  solution,  as  by  treating  with 
an  alcoholic  solution  of  caustic  potash.  It  crystallizes  from 
alcohol  in  orange-red,  orthorhombic  crystals.  Reducing  agents 
convert  it  into  hydrazo-benzene,  C6H5 .  NH .  NHC6H5.  Azo  com- 
pounds are,  in  general,  highly  colored,  and  many  of  them  are 
used  as  dyes.  Those  that  are  useful  in  this  way  are  deriva- 
tives of  the  simple  azo  compounds,  especially  those  containing 
the  amino  and  hydroxyl  groups.  Some  of  them  will  be  treated 
of  in  other  connections. 

Hydrazo-benzene,  C6H5 .  NH .  NH .  C6H5,  is  formed  by  re- 
duction of  azo-benzene.  It  is  made  by  reduction  of  nitro- 
benzene by  means  of  zinc  dust  in  alkaline  solution,  without 
isolating  the  azo-benzene  which  is  formed  as  an  intermediate 
product.  It  forms  colorless  laminae,  is  scarcely  soluble  in 
water,  but  easily  in  alcohol  and  ether.  Under  the  influence 
of  mineral  acids,  hydrazo-benzene  is  transformed  into  the  iso- 
meric  benzidine, 

C6H5.NH  C6H4.NH2 

I        — >•   I 

C6H5.NH  C6H 

Hydrazo-benzene  Benzidine 


PHENYLHYDRAZINE  297 

Reduction-products  of  nitro-benzene.  —  The  final  re- 
duction-product of  nitro-benzene  is  amino-benzene  or  aniline, 
but  by  regulating  the  conditions,  a  number  of  intermediate 
products  can  be  obtained.  In  addition  to  those  already  men- 
tioned there  are  two  others,  azoxy-benzene,  C6H5 .  N20 .  C6H5,  and 
phenyl-hydroxylamine,  C6H5 .  NH  (OH). 

The  following  table  will  serve  to  emphasize  the  relations  be- 
tween these  products  :  — 

C6H5.N02     C6H5.Nv          C6H5.N      C6H5.NH      C6H6.NH2 

I    >0  ||  I 

C6H5.N/         C6H5.N      C6H5.NH 

Nitro-benzene          Azoxy-benzene         Azo-benzene       Hydrazo-benzene  Aniline 

These  compounds  are  representatives  of  classes  the  members 
of  which  have  similar  structures  and  properties. 

HYDRAZINES 

Hydrazo-benzene  is  a  derivative  of  hydrazine,  NH2 .  NH2,  and 
may  be  called  symmetrical  diphenylhydrazine  in  view  of  the 
fact  that  the  two  phenyl  groups  contained  in  it  are  symmetric- 
ally distributed,  as  shown  by  the  formula,  C6H5 .  NH .  NH .  C6H5. 
The  simplest  representative  of  the  class  of  aromatic  hydrazines 
is  phenylhydrazine,  C6H5 .  NH .  NH2,  a  compound  which,  as  has 
been  seen,  has  played  an  important  part  in  the  investigation  of 
the  sugars. 

Phenylhydrazine,  CCH5 .  NH  .  NH2.  —  This  is  formed  by 
the  reduction  of  diazonium  salts  :  — 

C6H5 .  N2C1  +  4  H  =  C6H5 .  NH .  NH2 .  HC1. 

Benzene-diazonium  chloride  Phenylhydrazine  hydrochloride 

C6H5 .  NH .  NH2 .  HC1  +  NaOH  =  C6H5 .  NH  .  NH2  -f  NaCl  + 

H20. 

It  is  a  yellow  oil  which,  when  cooled,  forms  crystals  that  melt 
at  23°.     It  boils  at  233°.     It  finds  extensive  application  in 


298  DERIVATIVES    OF   THE   BENZENE   SERIES 

the  manufacture  of  antipyrine,  a  somewhat  complicated  com* 
pound  much  used  in  medicine. 

Phenylhydrazine  is  a  monacid  base,  and  forms  well-charac- 
terized salts.  It  reacts  with  aldehydes  and  with  ketones,  form- 
ing phenylhydrazones,  and  with  aldoses  and  ketoses,  forming 
phenylosazones  (see  p.  194). 

Methylphenylhydrazine,  C6H5  .  NCH3  .  NH2,  is  made  by 
treating  methylaniline  with  nitrous  acid  and  reducing  the 
nitroso  compound  thus  formed:  — 

H«  -^  C6H5  .  N  <          -+  C.H.  .  K  < 


With  ketoses  it  forms  osazones  ;  with  aldoses  it  forms  hydra- 
zones  but  not  osazones,  and,  therefore,  it  can  be  used  to  dis- 
tinguish between  ketoses  and  aldoses. 

SULPHONIC  ACIDS  OF  BENZENE,  ETC. 

The  methods  of  preparation  of  the  sulphonic  acids,  and  the 
relations  of  these  acids  to  the  hydrocarbons,  were  treated  of 
in  connection  with  the  paraffins.  Three  general  methods  for 
their  preparation  were  given.  These  are  :  — 

1.  Oxidation  of  the  mercaptans  ;  thus,  ethyl-sulphonic  acid 
is  formed  by  oxidation  of  ethyl-mercaptan  :  — 

C2H5  .  SH  +  3  0  =  C2H5  .  S03H. 

2.  Treatment  of  a  halogen  substitution-product  with  a  sul- 
phite :  — 

C2H5Br  +  Na2S03  =  C2H5  .  S03Na  +  NaBr. 

3.  Treatment  of  a  hydrocarbon  with  sulphuric  acid.     This 
method  is  not  applicable  to  the  paraffins,  but  is  the  one  used 
almost  exclusively  in  the  case  of  the  benzene  hydrocarbons. 
This  reaction  is  characteristic   of   the  aromatic   compounds 
Benzene-sulphonic  acid  is  formed  thus  :  — 

C6H6  +  H2S04  =  C6H5  .  S03H  +  H20. 


BENZENE-SULPHONIC    ACID  299 

Toluene-sulphonic  acid  is  formed  thus :  — 

PTT 
C6H5 .  CH3  +  H2S04  =  C6H4  <  g0  3H  +  H20. 

The  constitution  of  sulphonic  acids  is  discussed  on  p.  77. 

/  f  TT  \ 

Benzene-sulphonic  acid,  C6H6SO3  f  ij    5  >  SO2J.  — Thisi 

acid  is  made  by  treating  benzene  with  sulphuric  acid.  Simi- 
larly, and  more  easily,  toluene-sulphonic  acid,  C7H7 .  S03H,  is 
made  from  toluene. 

Experiment  62.  In  a  flask  bring  together  about  50CC  toluene  and 
100CC  concentrated  sulphuric  acid  (ordinary).  Heat  on  a  water-bath  and 
shake  until  most  of  the  toluene  is  dissolved.  Pour  the  contents  of  the 
flask  into  a  large  evaporating  dish  of  at  least  81  to  101  capacity,  contain' 
ing  41  to  51  water.  Heat  gently,  and  add  gradually,  stirring  meanwhile, 
finely-powdered  chalk,  until  the  solution  has  become  neutral.  Pas? 
through  a  muslin  filter  attached  to  a  wooden  frame,  and  wash  thor- 
oughly with  hot  water.  Afterwards  refilter  the  filtrate  through  a  paper 
filter.  Evaporate  to  quite  a  small  volume  (say  500CC  to  700CC),  and  filter 
from  gypsum.  In  solution  there  is  now  the  calcium  salt  of  the  sulphonic 
acid.  Add  just  enough  of  a  solution  of  sodium  carbonate  to  precipitate 
exactly  the  calcium  ;  filter  off  from  the  calcium  carbonate,  and  evaporate 
to  dryness,  finally,  on  the  water-bath.  To  prevent  caking  it  is  necessary 
to  stir  the  thick,  syrupy  mass.  When  it  is  nearly  dry,  it  is  best  to 
powder  it,  and  complete  the  drying  at  100°  to  120°  in  an  air-bath.  The 
sodium  salt  can  be  used  for  a  number  of  experiments. 

Experiment  63.  In  a  dry  evaporating  dish  mix  thoroughly  20s  of 
sodium  toluene-sulphonate  with  25s  of  phosphorus  penta-chloride,  by 
means  of  a  dry  pestle.  The  mass  becomes  semi-liquid  and  hot,  and 
hydrochloric  acid  is  given  off,  in  consequence  of  the  action  of  the 
moisture  of  the  air  on  the  chlorides  of  phosphorus.  Hence,  the  experi- 
ment should  be  performed  under  a  hood  or  out  of  doors.  The  reaction 
is  represented  by  the  equation,  — 

C7H7 .  S02ONa  +  PC15  =  C7H7.  S02C1  +  POC13  +  NaCl. 
After  the  action  is  over,  and  the  mass  cooled  down  to  the  ordinary 
temperature,  add  about  a  litre  of  cold  water.     Everything  will  dissolve 
except  the  sulphon-chloride,  C7H7.  SO2C1,  which  will  remain  as  a  heavy 
oil  at  the  bottom  of  the  vessel.    Pour  off  the  water,  add  about  500CC  oi 


300  DERIVATIVES   OF   THE  BENZENE   SERIES 

strong  ammonia,  and  let  stand.  The  chloride  will  thus  be  converted  into 
the  corresponding  sulphon-amide,  thus :  — 

C7H7.  S02C1  +  2  NH3  =  C7H7.  S02NH2  +  NH4C1. 

After  cooling,  filter  off  the  sulphon-amide ;  wash  well  with  cold  water, 
and  crystallize  from  water. 

NOTE  FOR  STUDENT.  —  Refer  back  to  what  was  said  regarding  the  acid 
chlorides  and  acid  amides,  paying  particular  attention  to  the  general 
methods  of  preparation  and  their  decompositions. 

Experiment  64.  Mix  208  potassium  cyanide  with  an  equal  weight 
of  dry  potassium  toluene-sulphonate,  and  distil  from  a  small  retort.  The 
distillate  is  impure  tolyl  cyanide,  C7H7.CN  :  — 

CIKO  >  s°2  +  KCN  =  °7H7 ' CN  +  K2S°8- 

Put  the  tolyl  cyanide  in  a  flask  of  300CC  to  400CC  capacity,  and  add  a  mix- 
ture of  50CC  water  and  150CC  ordinary  concentrated  sulphuric  acid.  Heat 
on  a  sand-bath  until  the  toluic  acid  begins  to  appear  in  the  form  of  fine, 
white  needles  in  the  neck  of  the  flask.  On  cooling,  the  acid  will  crystal- 
lize out.  Pour  off  the  liquid,  and  wash  with  cold  water.  Now  crystal- 
lize the  acid  once  or  twice  from  water.  When  pure,  paratoluic  acid 
melts  at  177°.  The  reaction  is  represented  by  the  following  equation  :  — 

C7H7.  CN  4  2  H2O  =  C7H7 .  C02H  +  NH3. 

Benzene-sulphonic  acid  itself  is  a  very  easily  soluble  sub- 
stance. It  is  a  strong  acid,  and  yields  a  series  of  salts  and 
other  derivatives. 

When  fused  with  potassium  hydroxide,  benzene-sulphonio 
acid  is  converted  into  phenol  (Exp.  65,  p.  304) :  — 

C6H5.  S03K  -f  KOH  =  C6H5.  OH  +  K2S03. 

By  further  treatment  of  benzene  with  fuming  sulphuric  acid 
a  benzene-disulphonic  acid  is  formed.  This  is  capable  of  the 
same  transformations  as  the  mono-sulphonic  acid. 

NOTE  FOR  STUDENT.  —  By  what  reaction  could  benzene-disulphonio 
acid  be  transformed  into  the  corresponding  dicarbonic  acid,  C6H4(CO2H)2? 
Suppose  the  product  obtained  were  meta-phthalic  acid,  what  conclusion 
could  be  drawn  with  reference  to  the  relation  of  the  two  sulpho  groups, 
S08H,  in  the  disulphonic  acid  ? 


HELIANTHIN  301 

Sulphanilic  acid,  C6H4<  _  _  L. .  —  Concentrated   sulphuric 

fc>U3±i 

acid  converts  aniline  into  aniline  sulphate,  C6H5NH3 .  HS04. 
When  this  is  heated  to  180°— 200°  it  is  converted  into  the 

para-sulphonic  acid,  C6H4  <  SQ  ^/  y  — 

C6H5.NH3.HS04  =  C6H4<^*  +H20. 

bU3±i 

Sulphanilic  acid  is  difficultly  soluble  in  cold  water,  more  easily 
in  hot  water.  It  crystallizes  from  a  solution  in  water  in  ortho- 
rhombic  plates. 

Like    taurine,  it  is  an  inner  ammonium  salt,  and  should, 

NTT 

therefore,  be  represented  thus,  C6H4<  cr>  3>.    It  is,  however, 

bL>3 

a  strong  acid,  while  taurine  is  neutral.  This  is  accounted  for 
by  the  fact  that  aniline  is  a  much  weaker  base  than  ethylamine. 
In  taurine  the  basic  portion  has  the  power  completely  to  neu- 
tralize the  acid  portion,  while  in  Sulphanilic  acid  this  is  not 
the  case.  Sulphanilic  acid  finds  extensive  application  in 
the  manufacture  of  dyes. 


Helianthin,  orange  III,  tropseolin  D,  is  an  example  of 
the  azo  dyes  already  referred  to.  It  is  formed  by  the  action 
of  benzene-diazonium  sulphonate  on  dimethyl-aniline.  The 
benzene-diazonium  sulphonate  is  made  from  Sulphanilic  acid  :  — 


(1)  C,H. 

Sulphanilic  acid  Benzene-diazonium  sulphonate 


Benzene-diazonium  Dimethyl-  Dimethyl-amino-azo-benzene 

sulphonate  aniline  sulphonate 

This  product  is  helianthin.     The  sodium  salt  is  orange  III 


302  DERIVATIVES    OF   THE   BENZENE   SERIES 

or  methyl  orange.  It  is  very  sensitive  to  acids  and  alkalies, 
and  is  used  as  an  indicator  in  acidimetry  and  alkalimetry. 
It  reacts  with  the  weakest  alkalies  and  is  not  affected  by 
carbonic  acid. 

Diphenylamine  orange,  tropseolin  OO,  is  another  ex* 
ample  of  the  azo  dyes.  It  is  made  by  the  action  of  diazotized 
sulphanilic  acid  on  diphenyl-amine  in  alkaline  solution  :  — 


S03         C6H5  S03Na 

Diphenyl-amine  orange 

PHENOLS,  OB  HYDROXYL  DERIVATIVES  OF  BENZENE,  ETC. 

The  hydroxyl  derivatives  of  the  paraffins  are  called  alcohols. 
As  will  be  remembered,  they  are  of  three  kinds,  each  of  which 
is  well  characterized.  These  are  :  — 

1.  Primary  alcohols,  of  which  ordinary  ethyl  alcohol  is  the 
commonest  example,  and  which,  when  oxidized,  yield  aldehydes 
and  then  acids  containing  the  same  number  of  carbon  atoms. 

2.  Secondary  alcohols,  which  by  oxidation  yield  acetones  and 
then  acids  containing  a  smaller  number  of  carbon  atoms. 

3.  Tertiary  alcohols,  which  by  oxidation  yield  neither  alde- 
hydes nor  acetones,  but  break  down  at  once,  yielding  acids 
with  a  smaller  number  of  carbon  atoms. 

The   primary  alcohols   were   shown   to   correspond  to   the 
fR  fE 

I  H  R 

formula  Cj  H    ;  the  secondary  to  C<  H    ;  and  the  tertiary  to 

R          I  HO  [HO 

R 

R    ;  or,  in  other  words,  the  primary  alcohols  .contain  the 

HO 

group  CH2oOH;  the  secondary,  the  group  CH.OH;  and  the 
tertiary,  the  group  C  .  OH. 


MON-ACID    PHENOLS  303 

Now,  the  simplest  hydroxyl  derivative  of  the  members  of 
the  benzene  series  is  phenol,  C6H5.OH,  or  benzene  in  which 
one  hydrogen  is  replaced  by  hydroxyl.  Representing  this 
compound  in  terms  of  the  accepted  benzene  hypothesis,  we 
have  the  formula 

OH 

HC/  \CH 


H 

According  to  this,  phenol  appears  to  be  allied  to  the  tertiary 
alcohols,  as  it  contains  the  group  C  .  OH,  and  not  CH2OH  nor 
CH.OH.  We  shall  see  that,  in  fact,  phenol  conducts  itself 
towards  oxidizing  agents  like  the  tertiary  alcohols.  It  yields 
neither  aldehydes  nor  ketones. 

All  compounds  which  contain  hydroxyl  in  the  place  of  the 
benzene-hydrogen  atoms  of  benzene  and  its  homologues  are 
called  phenols.  As  in  the  case  of  alcohols,  there  are  phenols 
containing  one  hydroxyl,  or  mon-acid  phenols;  those  contain- 
ing two  hydroxyls,  or  di-acid  phenols;  those  containing  three 
hydroxyls,  or  tri-add  phenols}  etc.  Some  of  these  are  familiar 
substances. 

MON-ACID  PHENOLS 

Phenol,  carbolic  acid,  C6H6O(C6H5OH).  —  Phenol  is  found 
in  small  quantities  in  the  urine.  It  is  formed  by  the  distilla- 
tion of  wood,  coal,  and  bones.  Hence,  it  is  a  constituent  of 
coal  tar,  and  from  this  it  is  prepared.  For  this  purpose  the 
heavy  oil  (see  p.  254)  is  treated  with  an  alkali  which  dissolves 
the  phenol.  From  the  solution  it  is  precipitated  by  hydro- 
chloric acid.  It  is  purified  by  distillation. 

Phenol  can  also  be  made  by  converting  nitro-benzene  into 
aniline  ;  then  into  diazo-benzene  ;  and  boiling  this  with  water 


304  DERIVATIVES   OF   THE   BENZENE   SERIES 

(see  Exp.  61  (&)) ;  and  by  fusing  a  salt  of  benzene-sulphonic 
acid  with  potassium  hydroxide. 

Experiment  65.  In  a  silver  (or  iron)  crucible,  or  evaporating  dish, 
melt  40s  to  50s  potassium  hydroxide,  after  adding  a  few  cubic  centimetres 
of  water.  Now  add  gradually  10s  finely-powdered  sodium  toluene-sulpho- 
nate,  obtained  in  Exp.  62,  stirring  constantly  with  a  silver  (or  iron)  spatula. 
Do  not  heat  to  a  very  high  temperature.  After  the  mass  has  been  kept  in 
a  state  of  fusion  for  one-quarter  to  one-half  an  hour,  let  it  cool.  Dissolve 
in  200CC  to  250CC  water,  and  acidify  with  hydrochloric  acid.  Notice  the 
odor  of  the  gases  given  off.  What  gas  do  you  detect  ?  When  the  liquid 
has  cooled  down,  extract  with  ether  in  a  glass-stoppered  cylinder.  From 
the  ether  extract  distil  the  ether  on  a  water-bath.  The  residue  is  impure 
cresol  (p.  309).  Phenol  can  be  detected  by  the  following  reactions,  for 
which  a  solution  in  water  should  be  prepared  :  — 

(a)  A  few  drops  of  ferric  chloride  solution  gives  a  beautiful  blue  color. 

(6)  Add  one-fourth  volume  of  ammonia,  and  then  a  few  drops  of  a 
dilute  solution  of  bleaching  powder.  A  blue  color  is  produced. 

(c)  Bromine  water  gives  a  yellowish-white  precipitate  of  tri-brom- 
phenol. 

The  reaction  which  takes  place  on  fusing  potassium  hydrox- 
ide and  potassium  benzene-sulphonate  together  is  represented 
by  the  equation,  — 

C6H5 .  S03K  +  KOH  =  C6H5 .  OH  +  K2S03. 

It  effects  the  replacement  of  the  group,  S03K,  by  hydroxyl. 
Phenol  is  made  by  this  method  on  the  large  scale. 

Phenol,  when  pure,  crystallizes  in  beautiful  colorless  ortho- 
rhombic  needles  that  melt  at  42°.  The  presence  of  a  little 
water  prevents  it  from  solidifying.  It  has  a  peculiar, 
penetrating  odor ;  boils  at  181° ;  is  difficultly  soluble  in 
water  (1  part  in  15  parts  water  at  ordinary  temperature); 
mixes  with  alcohol  and  ether  in  all  proportions;  and  is 
poisonous.  It  is  a  valuable  antiseptic,  and  finds  extensive 
application  as  a  disinfectant  and  in  the  manufacture  of  picric 
acid. 

An  aqueous  solution  of  phenol  is  colored  violet  by  a  little 
ferric  chloride. 


DIPHENYL-ETHEB  305 

Bromine  water  gives  a  precipitate  of  tri-brom-phenol  when 
added  to  a  water  solution  of  phenol. 

Phenol  is  not  soluble  in  alkaline  carbonates.  Its  acid  prop- 
erties are  not  strong  enough  to  enable  it  to  decompose  these 
carbonates.  On  the  other  hand,  it  forms  salts  with  the  alkalies 
and  with  several  strong  bases.  Among  these  may  be  men- 
tioned the  following  :  — 

Potassium  phenolate,  C6H5  .  OK,  made  by  dissolving  potassium 
in  phenol,  and  by  treating  phenol  with  a  solution  of  caustic 
potash. 

Barium  phenolate,  (C6H50)2Ba  +  2  H20,  made  by  dissolving 
phenol  in  baryta  water. 

Basic  lead  salt  of  phenol,  C6H6OPbOH,  made  by  dissolving 
lead  oxide  in  phenol. 

Phenol  also  forms  ethers,  of  which  the  methyl,  ethyl,  and 
diphenyl  ethers  may  serve  as  examples  :  — 


Methyl-phenyl  ether,  C7H8O          ^o.—  This  substance, 

also  called  anisol,  is  obtained  from  anisic  acid  (methoxy- 
benzoic  acid)  by  boiling  with  baryta  water.  It  is  made  also 
by  treating  potassium  phenolate,  C6H5OK,  with  methyl 

iodide  :  —  P  -u- 

C6H5OK  +  CH3I  =  $**«  >  0  +  KI. 

It  is  a  liquid  of  a  pleasant  odor. 

NOTE  FOR  STUDENT.  —  Compare  this  substance  with  ordinary  ether. 
What  method  analogous  to  that  above  mentioned  can  be  used  in  the 
preparation  of  ordinary  ether  ? 

Bthyl-phenyl  ether,  C8HIOO  >o,  ™  called  phenetol 


Diphenyl    ether,    C12H10O          5  >€>•  —  This    bears    to 


phenol  the  same  relation  that  ordinary  ether  bears  to  alcohol. 
With  acids,  phenol,  like  the  alcohols,  yields  ethereal  salts  in 
which  the  phenyl  group,  C6H5,  takes  the  place  of  a  metal 


306  DERIVATIVES   OF   THE   BENZENE   SERIES 

Among  the  compounds  of  this  class  which  phenol  forms  with 
organic  acids,  the  following  may  be  mentioned :  — 

Phenyl  acetate,  C8H802(CH3.  CO2-  C6H5).  — This  is  formed 
by  treating  phenol  with  acetyl  chloride. 

NOTE  FOR  STUDENT.  —  What  use  is  acetyl  chloride  put  to  as  a  reagent 
in  organic  chemistry  ?  Explain  its  use.  What  conclusion  can  be  drawn 
from  the  fact  that  acetyl  chloride  acts  upon  phenol,  replacing  one  hydrogen 
by  acetyl,  C2H3O  ? 

Substitution-products  of  phenol.  Phenol  is  very  susceptible 
to  the  action  of  various  reagents,  and  a  large  number  of  substi- 
tution-products have  been  made  from  it. 

Bromine  acts  upon  it  readily.  If,  for  example,  bromine 
water  is  added  to  a  water  solution  of  phenol,  tri-brom-phenol 
is  formed  and  precipitated. 

Nitro-phenols,  C6H5NO3(c6H4<Q^2).  —Dilute    nitric 

acid  acts  upon  phenol,  yielding  two  mono-nitro-phenols,  one 
of  which  belongs  to  the  ortho  series,  the  other  to  the  para 
series. 

Experiment  66.  Add  20s  phenol  to  a  mixture  of  80CC  water  and 
40C<5  ordinary  concentrated  nitric  acid  (sp.  gr.  1.34).  Stir,  with  cooling; 


Fig.  13. 


TRI-NITRO-PHENOL  307 

after  a  time,  pour  off  the  dilute  acid  from  the  oil.  Wash  with  water,  and 
put  it  into  a  flask,  with  about  a  litre  of  water,  arranged  as  shown  in 
Fig.  13.  Flask  A  holds  nothing  but  water  ;  while  the  oil,  together  with 
water,  are  in  B.  From  A  a  current  of  steam  is  passed  into  5,  which  is 
heated  by  means  of  a  lamp.  Yellow  crystals  pass  over  and  appear  in  the 
receiver,  while  a  non-volatile  substance  remains  behind  in  flask  B.  The 
volatile  substance  is  ortho-nitro-phenol  ;  the  non-volatile  is  para-nitro- 
phenol. 


Tri-nitro-phenol,  picric  acid,  C6H3N3O7 

This  is  formed  very  easily  by  the  action  of  strong  nitric  acid 
on  phenol. 

Experiment  67.  Add  We  phenol  slowly  to  10s  concentrated  nitric 
acid.  When  the  action  is  over,  add  30e  fuming  nitric  acid  and  heat  care- 
fully until  a  drop  put  in  water  forms  a  brittle  mass.  Dissolve  in  hot 
water,  and  purify  by  dissolving  in  potassium  carbonate,  and  evaporating 
to  crystallization. 

Picric  acid  crystallizes  in  yellow  leaflets  or  prisms,  has  a 
very  bitter  taste  (whence  the  name,  from  Tri/cpos,  bitter),  is 
poisonous,  decomposes  with  explosion  when  heated  rapidly. 
It  dyes  wool  and  silk  yellow. 

NOTE  FOR  STUDENT.  —  Is  there  any  analogy  between  tri-nitro-phenol 
and  tri-nitro-glycerin  ?  What  is  the  essential  difference  between  them  ? 

It  is  extensively  used  as  an  explosive  under  the  name  lyddite. 

One  of  the  most  interesting  properties  of  tri-nitro-phenol  is 
its  power  to  form  salts.  It  acts  like  a  strong  acid.  It  will 
thus  be  seen  that,  while  the  substance  C6H5.OH  has  only  very 
weak  acid  properties,  the  same  substance,  with  three  of  its 
hydrogens  replaced  by  nitro  groups,  C6H2(N02)3.  OH,  has 
strong  acid  properties.  In  the  salts,  which  have  the  general 
formula  C6H2(]Sr02)3.0M,  the  metal  replaces  the  hydrogen  of 
the  hydroxyl.  Among  them  may  be  mentioned  the  potassium 
salt  which  was  obtained  in  Exp.  67  ;  this  explodes  when  heated 
and  when  struck.  Ammonium  picrate,  C6H2(N02)3.ONH4,  is 
used  as  a  constituent  of  explosives. 


308  DERIVATIVES   OF   THE  BENZENE   SERIES 

OH 
Ammo-phenols,  C6H4  <  NH  .  —  The    ammo-phenols    are 


formed  by  reducing  the  nitro-phenols  by  means  of  tin  and 
hydrochloric  acid.  Met-amino-phenol  and  some  of  its  deriva- 
tives are  used  in  the  preparation  of  the  rhodamine  dyes. 

Par-amino-phenol,  used   under  the   name  of  rhodinol  as  a 
developer  in  photography,  yields  an  ethyl  ether,  p-phenetidine, 

C6H4<^2H6.    The  acetyl  derivative  of  this,  C«H4<°°2*!«          , 

JN-Ha  -Nri.CU.CHa 

is  extensively  used  in  medicine  under  the  name  phenacetin  as 
an  antipyretic  and  antineuralgic. 

OH 

Phenol-sulphonic  acids,  C6H4<  a/~  „.  —  When  phenol  is 


treated  with  sulphuric  acid,  the  ortho  and  para  sulphonic  acids 
are  formed.  At  low  temperatures  the  ortho  acid  is  formed  in 
larger  quantity  than  the  para  acid.  The  ortho  acid  is  readily 
converted  into  the  para  acid  by  heat,  so  that,  at  a  compara- 
tively high  temperature,  the  para  acid  is  the  principal  product. 
The  change  of  the  ortho  acid  to  the  para  takes  place  even  when 
its  water  solution  is  boiled.  A  mixture  of  the  ortho  and  the 
para  acids  is  used  in  water  solution  as  an  antiseptic  under  the 
name  aseptol. 

Phenyl-mercaptan,  ^ 

Phenyl  hydrosulphide,   >-  C6H6S(C6H5.SH).  —  This  bears 

Thiophenol,  ) 

the  same  relation  to  phenol  that  rnercaptan  bears  to  alcohol. 
It  can  be  made  by  reducing  benzene-sulphon-chloride.  This 
reduction  is  effected  by  first  making  the  sulphon-chloride, 
C6H5.S02C1  (Exp.  63),  and  then  treating  this  with  nascent 
hydrogen. 

NOTE  FOR  STUDENT.  —  What  is  the  effect  of  oxidizing  the  mercaptans? 

It  can  be  made,  also,  by  treating  phenol  with  phosphorus 
pentasulphide,  the  effect  of  this  reagent  being  to  substitute 
sulphur  for  oxygen. 


THYMOL  309 

NOTE  FOR  STUDENT.  —  What  analogy  is  there  between  the  action  of 
phosphorus  pentachloride  and  of  phosphorus  pentasulphide  on  compounds 
containing  oxygen  ? 

Phenyl-mercaptan  is  a  liquid,  with  a  very  disagreeable  odor. 
It  forms  a  crystallized  mercury  compound,  (C6H6S)2Hg. 


/  p-TT  \ 

Cresols,  C7H8O(  C6H4  <  ^      ).  —  There   are  three  cresols, 


or  hydroxyl  derivatives  of  toluene,  of  the  formula  C6H4  < 

They  are  all  found  in  coal  tar,  and  the  tars  from  pine  and  beech 
wood.  When  mixed  together,  it  is  difficult  to  separate  them. 
To  obtain  them  in  pure  condition,  it  is  therefore  best  to  make 
them  from  the  three  toluidines,  or  from  the  three  sulphonic 
acids  of  toluene. 

NOTE  FOR  STUDENT.  —  Give  the  equations  representing  the  reactions 
involved  in  passing  from  the  three  toluidines  to  the  cresols,  and  from  the 
three  toluene-sulphonic  acids  to  the  cresols. 

The  cresols  resemble  phenol  very  closely. 

Creosote  is  a  mixture  of  chemical  compounds  contained  in 
wood  tar.  It  contains  the  cresols.  Coal-tar  creosote  consists 
largely  of  phenols. 

f  cm 

Thymol,      isopropyl-meta-cresol,      CeHs  I  OH  (w)  -1  — 

I  C3H7(p) 

This  phenol  is  contained  in  oil  of  thyme,  together  with  cy- 
mene,  and  is  made  artificially  from  nitro-cuminic  aldehyde, 

rCHO 
C6H3  J  N02  (»»).     When  this  is  reduced  it  gives  an  amino  deriva- 

t 


1  Formulas  of  this  kind  serve  very  well  to  indicate  the  relations  of  the  groups  and 
atoms  contained  in  benzene  derivatives.  This  one,  for  example,  indicates  that  the 
hydroxyl  is  in  the  meta  position  (m)  to  methyl;  while  the  propyl  is  in  the  para 
position  (p)  to  methyl.  For  di-substitution  products,  such  formulas  may  also 

CH 

be    used.      Thus,    the    three    toluidines    may    be    represented    by    C6H4<NH8/O)» 
€HS  CH8 

NH  (m),   a»d  C6H4  <  - 


310  DERIVATIVES   OF   THE   BENZENE  SERIES 

rCH3 

tive  of  cymene,  C6H3  ]  NH2  ,  which  can  be  converted  into  thymol 
lcH 


through  the  diazo  compound.  It  forms  large  monoclinic  crys- 
tals, which  melt  at  50°.  It  has  a  pleasant  odor,  like  that  of 
the  oil  of  thyme.  Treated  with  phosphorus  pentoxide,  it 
yields  meta-cresol  and  propylene,  C3H6;  while,  when  treated 
with  phosphorus  pentasulphide,  it  yields  cymene.  These  two 
reactions  indicate  that  the  groups  contained  in  thymol  bear  to 
each  other  the  relations  indicated  by  the  formula  given  above. 
It  is  one  of  the  two  theoretically  possible  hydroxyl  derivatives 
of  cymene.  The  other  one,  carvacrol,  has  the  hydroxyl  in  the 
ortho  position  relative  to  methyl.  It  has  been  made  from 
the  corresponding  cymene-sulphonic  acid  ;  is  found  in  nature 
in  the  ethereal  oil  of  Origanum  hirtum;  and  can  be  made  from 
earvone,  or  the  oil  of  caraway,  by  heating  it  with  glacial  phos- 
phoric acid  or  with  caustic  potash. 

DI-ACID  PHENOLS 
The    three    theoretically    possible     di-hydroxyl    benzenes, 

OTT 

C6H4<,  are  all  well  known. 


Pyrocatechol,  \  r«  TT  n  (  r*  TT  ^  OH     ^ 

Ortho-di-hydroxy-benzene,  /  °  AU2  V°6^4  <  OH(<>)  J 


This  substance  is  a  frequent  product  of  the  dry  distillation  of 
natural  substances,  —  as  of  catechu,  morintannic  acid,  etc.,  — 
and  of  the  melting  of  resins  with  caustic  potash.  It  can  be 
made  by  fusing  ortho-chlor-phenol  or  ortho-phenol-sulphonic 
acid  with  caustic  potash.  It  forms  crystals,  which  melt  at 
104°.  It  is  easily  soluble  in  water,  alcohol,  and  ether. 

The  dilute  solution  in  water  gives  with  ferric  chloride  a 
dark  green  color,  which  becomes  violet  on  the  addition  of  a 
jfittle  of  a  very  dilute  solution  of  sodium  carbonate. 

It  reduces  silver  nitrate  in  solution  in  cold  water.  It  is 
used  in  photography. 


DI-ACID    PHENOLS  311 


Guaiacol,  monomethyl-pyrocatechol,    C6H4  <  _  __   3.  — 

OH(o) 

This  substance  was  first  found  in  guaiac  resin.  Hence  its 
name.  It  is  formed  in  considerable  quantity  in  the  distilla- 
tion of  wood,  especially  beech  wood.  It  is  made  syntheti- 
cally by  treating  the  mono-potassium  salt  of  pyrocatechol  with 
methyl  iodide.  It  is  a  liquid  that  solidifies  at  28.5°  and  boils 
at  205°.  The  carbonate,  CO(OC6H4  .  OCH3)2,  has  been  recom- 
mended as  a  remedy  in  tuberculosis. 


Veratrol,  dimethyl-pyrocatechol,  C6H4  <  8,  is  formed 

OCH.3 

by  treating  the  di-potassium  .salt  of  pyrocatechol  with  methyl 

(CO2H 
iodide  and  by  distilling  veratric  acid,  C6H3  4  OCH3,  with  lime. 


Resorcinol,  I  n  TT  o  /  n  TT  ^  OH     ^ 

Meta-di-hydroxy-benzene,  ^        h  V      ^  <  OH(m)  )  ' 
Resorcinol  is  formed  by  the  melting  of  a  number  of  resins  with 
caustic  potash,  as   of  galbanum,   sagapenum,  asafoetida,  etc. 
It  is  made,  also,  by  melting  meta-iodo-phenol  or  meta-benzene- 
disulphonic  acid  with  caustic  potash. 

It  crystallizes  from  water,  usually  in  thick,  orthorhombic 
prisms.  Melting-point,  118°' 

With  ferric  chloride,  the  water  solution  gives  a  dark  violet 
color.  Heated  for  a  few  minutes  with  phthalic  anhydride  in  a 
test-tube,  a  yellowish-red  mass  is  formed.  When  this  is  added 
to  dilute  caustic  soda,  a  solution  with  remarkable  fluorescence 
is  obtained.  The  explanation  of  this  reaction  will  be  given 
under  the  head  of  Tri-phenyl-methane,  when  the  phthaleins 
will  be  described. 

Eesorcinol  is  used  largely  in  the  manufacture  of  certain  dyes, 
and  is  therefore  manufactured  on  the  large  scale. 

Heated  with  sodium  nitrite  resorcinol  gives  a  deep  blue 
dye.  This  is  soluble  in  water  and  the  solution  is  turned 

I 


312  DERIVATIVES    OF   THE   BENZENE   SEKIES 

red  by  acids.     It  is  called  lacmoid  and  is  used  as  an  indi- 
cator. 


compound  is  formed  by  the  action  of  nitric  acid  on  resovcinol, 
and  on  those  resins  which  give  resorcinol  when  treated  with 
caustic  potash.  It  closely  resembles  picric  acid.  Heated  with 
bromine  and  acetic  acid,  it  yields  the  substance  known  as 
brompicrinj  which  has  the  formula  C(N02)Br3. 

Hydroquinol,  \  r  TT  n  Ir  TT  ^  OH     ^ 

Para-di-hydroxy-benzene,    I  °6±leU2  (^±±4  <  OH(/))  ;  • 

Hydroquinol  is  formed  by  the  oxidation  of  quinic  acid,  by 
reduction  of  quinone  (which  see),  by  means  of  sulphur  dioxide, 
by  fusing  para-iodo-  phenol  with  caustic  potash,  etc. 

It  is  a  crystallized  substance  which  melts  at  169°;  easily 
soluble  in  alcohol,  ether,  and  hot  water. 

Oxidizing  agents,  such  as  ferric  chloride,  chlorine,  etc.,  convert 
it  into  quinone.  It  is  used  in  photography  as  a  "  developer." 


It  would  lead  too  far  to  discuss  here  the  reactions  which 
have  been  made  use  of  for  the  purpose  of  determining  to  which 
series  each  of  the  three  di-hydroxy-benzenes  belongs.  The 
principle  involved,  however,  is  simple.  Either  these  substances 
must  be  converted,  directly  or  indirectly,  into  others,  in  regard 
to  the  relation  of  whose  groups  we  have  evidence;  or  sub- 
stances, the  relation  of  whose  groups  is  known,  must  be  con- 
verted into  the  di-hydroxy-benzenes.  The  reactions  employed 
for  effecting  the  conversions  are  mainly  those  which  have 
already  been  studied ;  viz.,  the  formation  of  amino  compounds 
from  nitro  compounds  by  reduction;  the  formation  of  diazo  com- 
pounds from  amino  compounds  ;  the  formation  of  (1)  hydroxy? 
derivatives,  (2)  chlorine,  bromine,  or  iodine  derivatives,  from 
the  diazo  compounds ;  and  the  formation  of  hydroxyl  deriva- 
tives from  sulphonic  acids. 

* 


TRI-ACID   PHENOLS  313 


two  coloring  matters,  known  as  archil  and  litmus,  which  are 
made  from  different  lichens  by  exposing  them  in  powdered 
condition  in  ammoniacal  solution  to  the  action  of  air.  Archil 
contains  a  substance  called  orcein,  which  can  be  made  from 
orcinol  by  treating  it  with  ammonia  in  contact  with  the  air. 
Orcinol  is  contained  in  several  lichens.  It  is  formed,  also,  by 
melting  aloes  with  caustic  potash,  and  by  melting  1,  3,  5-chlor- 
toluene-sulphonic  acid  with  caustic  potash.  The  last  reaction 
shows  that  orcinol  is  1,  3,  5-di-hydroxy-toluene. 

Orcinol  crystallizes  in  large,  colorless,  monoclinic  prisms 
which  turn  red  in  the  air.  Ferric  chloride  colors  the  aqueous 
solution  a  blue  violet. 

Treated  with  ammonia  in  moist  air,  it  is  converted  into 
orcein,  CasH^NaO;,  a  substance  which  dissolves  in  alkalies, 
forming  beautiful  red  solutions. 

Orcinol  is  manufactured  on  the  large  scale,  and  then  con- 
verted into  orcein,  which  is  used  as  a  dye. 

Litmus  is  obtained  from  the  lichens  Roccella  and  Lecanora  by 
treating  them  with  ammonia  and  potassium  carbonate.  Com- 
mercial litmus  is  made  by  mixing  the  concentrated  solution 
of  the  potassium  salt  with  chalk  or  gypsum. 


TRI-ACID  PHENOLS 


Pyrogallol,  pyrogallic  acid,  1  c 
Tri-hydroxy-benzene,  J    8    6    a 


fOH(l) 
C6H3  OH(2) 


IOH(3) 

Pyrogallic  acid  is  formed  by  dry  distillation  of  gallic  acid,  the 
reaction  being  analogous  to  that  by  which  benzene  is  produced 
by  distillation  of  benzoic  acid  :  — 


C6H5.C02H 

Benzole  acid  Benzene 


314  DERIVATIVES    OP   THE   BENZENE    SERIES 


C6H8{  £"'3  =  C6H3(OH)3  +  C02. 

2  Pyrogallol 

Gallic  acid 

It  is  formed  also  when  one  of  the  chlor-phenol-sulphonic  acids 
is  fused  with  caustic  potash :  — 

[OH  (i)    KOH         [OH 

C6H3  Cl      (2)  +  KOR  =  C6H3  OH  +  KC1  +  K2S03. 
lS03K(3)  I  OH 

Potassium  chlor-phenol-  Pyrogallol 

sulphonate 

It  crystallizes  in  laminae  or  needles ;  melts  at  132-133° ;  is 
easily  soluble  in  water,  ether,  and  alcohol.  In  alkaline  solu- 
tion it  absorbs  oxygen  rapidly  and  becomes  brown.  On  account 
of  this  power  to  absorb  oxygen  it  is  used  in  gas  analysis.  It 
is  poisonous.  With  a  solution  containing  a  ferrous  and  a  ferric 
salt  it  gives  a  blue  color. 

Most  of  the  phenols  give  color  reactions  with  ferric  chloride, 
and  most  of  them  change  color  in  the  air.  These  changes  in 
color  are  undoubtedly  due  to  the  action  of  oxygen.  Towards 
oxidizing  agents  they  are  all  unstable,  most  of  them  breaking 
down  readily  and  yielding  as  the  chief  product  of  oxidation, 
carbon  dioxide.  In  general,  the  larger  the  number  of  hydroxyl 
groups  contained  in  a  phenol,  the  less  stable  it  is.  It  will  be 
seen  that  these  same  statements  hold  good  for  the  hydroxy- 
acids  of  the  benzene  group,  of  which  gallic  acid  and  salicylic 
acid  are  examples. 

f          fOH(l)] 
Phloroglucinol,  C6H3(OH)3  j  O6HS|  OH(3)  j .  —  This  phenol 

IOH(5)J 

was  first  obtained  from  phloretin,  which  is  one  of  the  products 
of  decomposition  of  a  glucoside  (see  G-lucosides),  phloridzin. 
It  can  be  obtained  also  from  other  glucosides,  and  from  several 
resins.  Resorcinol  gives  it  when  fused  with  potassium  hydrox- 
ide, as  does  1,  3,  5-benzene-trisulphonic  acid. 

In  some  of  its  reactions  phloroglucinol  acts  like  a  tri-hydroxy 


ALCOHOLS   OF   THE   BENZENE   SERIES  315 

benzene,  in  others  it  acts  as  if  it  contained  three  carbonyl 
groups,  CO.  Thus,  for  example,  on  the  one  hand,  it  gives  a 
tri-methyl-ether,  C«,H8(OCH8)$,  and,  on  the  other  hand,  with  hy- 
droxylamine  it  gives  a  tripxime,  C6H6(.NOH)3.  In  the  present 
state  of  our  knowledge  we  can  only  conclude  that  in  contact 
with  some  reagents  it  actually  is  tri-hydroxy-benzene,  while  in 
contact  with  others  it  is  tri-keto-hexa-methylene.  The  two 
conditions  are  represented  by  the  formulas  :  — 


CH2 


OH 

Tri-hydroxy-benzene  Tri-keto-hexa-methylene 

This  is  another  example  of  tautomerisin  already  illustrated 
by  hydrocyanic  acid  and  by  uric  acid. 

ALCOHOLS  OF  THE  BENZENE  SERIES 

The  phenols  are  those  hydroxyl  derivatives  of  the  benzene 
hydrocarbons,  which  contain  the  hydroxyl  in  the  place  of  one 
or  more  of  the  six  benzene  hydrogens.  But  just  as  there  are 
two  classes  of  halogen  substitution-products  of  toluene,  in  one 
of  which  the  substitution  has  taken  place  in  the  benzene  resi- 
due, and  in  the  other  in  the  marsh-gas  residue,  as  indicated  in 
the  two  formulas,  — 

C6H4C1 .  CH3      and      C6H5 .  CH2C1, 

so,  also,  there  are  two  classes  of  hydroxyl  derivatives :  (1)  the 
phenols,  and  (2)  those  in  which  the  hydroxyl  is  in  the  marsh- 
gas  residue.  The  simplest  example  of  the  second  class  corre- 
sponds to  the  formula,  C6H5 .  CH2 .  OH.  It  is  isomeric  with  the 
cresols,  C6H4 .  OH .  CH3,  and  has  entirely  different  properties. 
While  the  cresols  are  the  true  homologues  of  phenol,  the  new 
substance  is  methyl  alcohol  in  which  one  of  the  hydrogens 


316  DERIVATIVES    OF   THE   BENZENE   SERIES 

of  the  ra  ethyl  has  been  replaced  by  phenyl,  C6H5.     It  may 

•       fC6H6 

I  TT 

be  represented  by  the  formula,  C    H     t    which    makes    its 


CH 


TT 

analogy  to  ethyl  alcohol,  c  |  H     >  apparent. 

I-OH 

Benzyl  alcohol,  C7H8O(C6H5.  CH2OH).  —  Benzyl  alcohol 
or  phenyl  carbinol  is  found  in  nature  in  the  balsams  of  Peru 
and  Tolu,  and  in  storax.  In  these  substances  it  is,  for  the 
most  part,  in  combination  with  benzoic  or  cinnamic  acid.  It  is 
made  by  treating  the  oil  of  bitter  almonds,  which  is  the  corre- 
sponding aldehyde,  with  nascent  hydrogen  :  — 

C6H5  .  CHO  +  H2  =  C6H5  .  CH2  .  OH. 

Oil  of  bitter  almonds  Benzyl  alcohol 

It  is  also  made  by  replacing  the  chlorine  in  benzyl  chloride, 
C6H5.  CH2C1,  by  hydroxyl,  just  as  methyl  alcohol  is  made  from 
methyl  chloride  by  a  similar  replacement.  In  the  case  of 
benzyl  chloride  this  can  be  effected  even  by  boiling  for  a  long 
time  with  water  :  — 

C6H5.  CH2C1  +  H20  =  C6H5  .  CH2OH  +  HC1. 

Benzyl  alcohol  is  a  colorless  liquid  with  a  pleasant  odor.  It 
boils  at  206.5°.  It  dissolves  with  difficulty  in  water,  and  is 
soluble  in  alcohol  and  ether. 

NOTE  FOR  STUDENT.  —  Notice  the  great  difference  between  the  boiling- 
point  of  methyl  alcohol  and  that  of  phenyl-methyl  alcohol. 

Oxidizing  agents  convert  the  alcohol,  first,  into  the  oil  of 
bitter  almonds  or  benzoic  aldehyde,  and  then  into  benzoic  acid. 
The  relations  between  the  three  substances  are  like  those  be- 
tween any  primary  alcohol  and  the  corresponding  aldehyde 
and  acid,  as  shown  by  the  formulas  :  — 

C6H5.CH2OH;         C6H5.CHO;         C6H5.C02H. 

Benzyl  alcohol  Benzoic  aldehyde  Benzoic  acid 


BENZYL   ALCOHOL  317 

Hydriodic  acid  converts  benzyl  alcohol  into  toluene:  — 
C6H5.  CH2OH  +.2HI  =  C6H5 .  CH3  +  H20  +  2 1. 

Benzyl  alcohol  conducts  itself,  in  most  respects,  like  the 
primary  alcohols  of  the  methyl  alcohol  series.  A  large  number 
of  its  derivatives  have  been  made  and  studied.  Among  them 
are  ethereal  salts,  of  which  benzyl  acetate,  CH3 .  CO .  OC7H7,  and 
benzyl  nitrate,  N02.OC7H7,  may  serve  as  examples;  ethers,  of. 
which  the  methyl  ether,  C6H3.CH2.O.CH3,  and  the  phenyl  ether, 
C6H5. CH2 .  OC6H5,  are  good  examples ;  and  substitution-products, 
of  which  chlor-benzyl  alcohol,  C6H4C1.CH2OH,  and  nitro-benzyl 
alcohol,  C6H4(N02).CH2OH,  are  examples. 

These  substitution-products  are  not  made  by  direct  treatment 
of  the  alcohol  with  the  substituting  agents,  but  by  starting  with 
the  corresponding  substituted  toluene.  Thus,  chlor-benzyl 
alcohol  is  made  from  chlor-toluene,  C6H4C1.CH3,  by  first  con- 
verting this  into  chlor-benzyl  chloride,  C6H4C1 .  CH2C1,  and  then 
replacing  the  chlorine  of  the  group  CH2C1  by  hydroxyl.  By 
oxidation  the  substituted  benzyl  alcohols  yield  the  correspond- 
ing substituted  benzoic  acid:  — 

C6H4C1 .  CH2OH         +  02  =  C6H4C1 .  C02H         +  H20. 

Chlor-benzoic  acid 

C6H4(N02).CH2OH  +  02=  C6H4(N02)C02H  +  H20. 

Nitro-benzoic  acid 

Very  few  of  the  alcohols  analogous  to  benzyl  alcohol  have 
been  prepared.  Plainly,  the  homologues  may  be  of  two  kinds : 

1.  Those  which  are  phenyl  derivatives  of  the  alcohols  of  the 
methyl  alcohol  series.  Of  this  class,  phenyl-ethyl  alcohol, 
C6H5.CH2.CH2OH,the  isomeric  substance  C6H5.CH.  OH. CH3, 
and  phenyl-propyl  alcohol,  C6H5.CH2.CH2.CH2OH,  are  exam- 
ples. Phenyl-propyl  alcohol  is  of  special  interest  on  account 
of  its  connection  with  cinnamic  acid  (which  see),  which  has 
come  into  prominence  since  it  has  been  shown  to  be  closely  re- 
lated to  the  interesting  substances  of  the  indigo  group.  It 


318  DERIVATIVES   OF   THE  BENZENE   SERIES 

occurs  in  storax  in  the  form  of  an  ethereal  salt,  which  will  be 
treated  of  more  fully  under  the  head  of  Cinnainic  Acid. 

2.  Those  which  are  derivatives  of  xylene,  mesitylene,  etc., 
in  the  same  sense  that  benzyl  alcohol  is  a  derivative  of  toluene. 
The  following  belong  to  this  class  :  — 


Tolyl-carbinol  ..... 

and          Cuminyl  alcohol   .... 

n7> 

which  is  made  from  cuminol,  an  aldehyde  found  in  the  oil  of 
cumin. 

ALDEHYDES  OF  THE  BENZENE  SERIES 

The  aldehydes  of  this  group  are  closely  related  to  the  alco- 
hols just  considered.  The  simplest  one  is  the  oil  of  bitter 
almonds,  or  benzoic  aldehyde,  C7H60. 

Oil  of  bitter  almonds,)^  ,-..  n,r  w    f^rr^       TI^C,  0  ^ 
Benzoic  aldehyde,  j  C'H'°  ^H*  -  OI 

stance  occurs  in  combination  in  amygdalin,  which  is  found  in 
bitter  almonds,  laurel  leaves,  cherry  kernels,  etc.  Amygdalin 
belongs  to  the  class  of  bodies  known  as  glucosides,  which  break 
up  into  a  glucose  and  other  substances.  Amygdalin  itself, 
under  the  influence  of  emulsin,  which  occurs  with  it  in  the 
plants,  breaks  up  into  benzoic  aldehyde,  hydrocyanic  acid,  and 
dextrose  :  — 


u  +  2  H20  =  C7H60  +  CNH  +  2  C6H1206. 

Amygdalin  Benzoic  aldehyde  Glucose 

Benzoic  aldehyde  can  be  made  : 

1.  By  oxidizing  benzyl  alcohol  :  — 

C6H5  .  CH2OH  +  0  =  C6H5  .  CHO  +  H20. 

2.  By  distilling  a  mixture  of  calcium  benzoate  and  calcium 
formate  :  — 


CUMINIC   ALDEHYDE  319 

C6H5.cof6Mj 

H  .  JCOOM!  =  CeH 

3.  By  treating  benzoyl  chloride  with  nascent  hydrogen  :  — 

C6H5  .  COC1  +  H2  =  C6H5  .  CHO  +  HC1. 

4.  By  treating  benzal  chloride  with  water  and  milk  of  lime 
under  pressure  :  — 

C6H5.  CHC12  +H20  =  C6H5  .  CHO  +  2  HC1. 

NOTE  FOR  STUDENT.  —  Refer  to  the  general  methods  for  the  prepara- 
tion of  aldehydes.  Which  of  the  above  reactions  are  used  for  the 
preparation  of  aldehydes  in  general  ?  Which  of  the  reactions  throw  light 
upon  the  nature  of  aldehydes,  and  their  relation  to  alcohols  ? 

Benzoic  aldehyde  is  prepared  either  from  bitter  almonds, 
which  yield  about  1.5  to  2  per  cent  ;  or  from  benzal  chloride. 
On  the  large  scale  it  is  prepared  by  treating  benzyl  chloride 
with  lead  nitrate  :  — 

2  C6H5  .  CH2C1  +  Pb(lsr03)2  =  PbCl2  +  2  C6H5  .  CHO  +  2  HNO2  ; 

or  from  benzal  chloride  (see  reaction  4  above). 

Benzoic  aldehyde  is  a  liquid  having  a  pleasant  characteristic 
odor.  It  boils  at  179°;  is  difficultly  soluble  in  water;  is  not 
poisonous. 

It  unites  with  oxygen  to  form  benzoic  acid  ;  with  hydrogen 
to  form  benzyl  alcohol  ;  with  hydrogen  sulphide,  ammonia, 
ammonium  sulphide,  alcohols,  acids,  anhydrides,  and  ketones. 
In  short,  its  powers  of  combination  with  other  substances  are 
almost  unlimited.  Hence,  a  very  large  number  of  derivatives 
are  known. 


Cuminic  aldehyde,  cuminol,  C10H12of  C6H4  <  S?P    V 

\  vaa.7(p)J 


This  aldehyde  occurs  in  oil  of  cumin,  from  which  it  is  made. 
It  is  a  liquid  with  the  odor  of  the  oil  of  cumin.  Its  reactions 
are  like  those  of  benzoic  aldehyde. 


320  DERIVATIVES    OF   THE   BENZENE   SERIES 

Benzaldoximes,  C6H5 .  CH :  N  .  OH.  —  Hydroxylamine  re- 
acts with  benzole  aldehyde  as  it  generally  reacts  with  aldehydes, 
forming  an  oxime  :  — 

C6H5.  CHO  +  H2NOH  =  C6H5 .  CH :  N.  OH  +  H20. 

This  appears  first  as  an  oil,  but  when  purified  it  forms  long, 
lustrous  prisms,  melting  at  35°. 

When  hydrochloric  acid  gas  is  conducted  into  an  ether  solu- 
tion of  the  above  oxime,  a  hydrochloride  is  precipitated,  and 
when  this  is  treated  with  sodium  carbonate,  a  new  oxime, 
isomeric  with  the  above,  is  obtained.  This  crystallizes  from 
ether  in  thin,  lustrous  needles,  and  melts,  when  rapidly  heated, 
at  125°.  By  long-continued  heating,  however,  it  is  converted 
into  the  oxime  melting  at  35°. 

These  two  oxirnes  are  regarded  as  stereoisomeric.  In  terms 
of  the  conceptions  of  stereochemistry  they  should  be  represented 
by  the  formulas :  — 

C6H5  -  C  -  H  and  C6H5  -  C  -  H 

II  II 

HO  -  N  N  -  OH 


or  *— K  and 


[For  an  explanation  of  the  significance  of  these  formulas, 
especially  as  far  as  the  nitrogen  atom  is  concerned,  see  p.  295.] 

The  one  with  the  hydrogen  atom  and  the  hydroxyl  on  oppo- 
site sides  is  called  benz-anti-aldoxime ;  the  one  with  the  hydro- 
gen atom  and  the  hydroxyl  on  the  same  side  is  called  benz- 
syn-aldoxime.  The  %one  that  melts  at  125°  easily  loses  water 
and  forms  phenyl  cyanide  or  benzonitril,  C6H5CN.  The  other 
does  not.  It  is  believed  that  the  one  that  loses  water  and 


BENZOIC    ACID  321 

yields  the  nitril  when  heated  with  acetic  anhydride  is  the  syn- 
oxime,  as  in  this  form  the  hydrogen  and  hydroxyl  appear  to  be 
so  situated  that  they  can  unite  to  yield  water,  whereas  this  is 
not  the  case  in  the  anti-form.  According  to  this  the  stable 
form,  the  one  most  easily  obtained,  is  the  anti-oxime.  Phe- 
nomena of  this  kind  have  been  extensively  studied  and  the 
ideas  here  set  forth  rest  upon  a  broad  foundation  of  experi- 
mental evidence. 

ACIDS  OF  THE  BENZENE  SERIES 

The  simplest  of  these  acids  is  benzoic  acid,  which  bears  to 
benzene  the  same  relation  that  acetic  acid  bears  to  marsh-gas. 
It  is  the  carboxyl  derivative  of  benzene.  The  homologous 
acids  are  derivatives  of  the  homologous  hydrocarbons.  There 
are  monobasic,  dibasic,  tribasic,  and  even  hexabasic  acids,  but 
the  number  actually  known  is  small. 

MONOBASIC  ACIDS,  CnH2n_802 

Benzoic  acid,  C7H6O2(C6H5 .  CO2H) — Benzoic  acid  occurs 
in  gum  benzoin,  in  the  balsams  of  Peru  and  Tolu,  and  in 
combination  with  amino-acetic  acid  or  glycine  in  the  urine  of 
herbivorous  animals.  It  can  be  made  in  many  ways,  the  most 
important  of  which  are  given  below :  — 

1.  By  oxidation  of  benzyl  alcohol  or  any  alcohol  which  is  a 
phenyl  derivative  of  an  alcohol  of  the  methyl  alcohol  series. 
The  common  condition  in  all  these  alcohols  is  the  presence  of 
the  difficultly  oxidizable  residue,  C6H5,  in  combination  with  an 
easily  oxidizable  residue  of  an  alcohol  of  the  marsh-gas  series :  — 

C6H5 .  CH2OH  gives  C6H5 .  C02H ; 

C6H5 .  CH2 .  CH2OH  «     C6H5 .  C02H ; 

C6H5 .  CH2 .  CH2 .  CH2OH      "     C6H5 .  C02H,  etc. 

2.  By  oxidation  of  benzoic  aldehyde,  and  the  aldehydes  of 
the  other  alcohols  referred  to  in  the  preceding  paragraph. 

3.  By  oxidation  of  all  benzene  hydrocarbons  which  contain 


322  DERIVATIVES   OF   THE   BENZENE    SERIES 

but  one  residue  of  the  marsh-gas  series.  Attention  has  already 
been  called  to  this  fact  (see  p.  270). 

4.  By  treating  cyan-benzene   (phenyl  cyanide,  benzo-nitril) 
with  sulphuric  acid  (see  Exp.  64,  p.  300)  :  — 

C6H5CN  +  2  H20  =  C6H5  -  C02H  +  NH3. 

5.  By  treating  benzene  with  carbonyl  chloride  in  the  pres- 
ence of  aluminium  chloride :  — 

C6H6  +  COC12  =  C6H5  •  COC1  +  HC1 ; 

C6H5  •  COC1  +  H20  =  C6H5  •  C02H  +  HC1. 

A  reaction  similar  to  this  is  of  extensive  application  in  the 
preparation  of  some  hydrocarbons.  It  will  be  treated  of  more 
fully  under  the  head  of  Tri-phenyl-methane. 

6.  By  treating  benzene  with  carbon  dioxide  in  the  presence 
of  aluminium  chloride :  — 

C6H6  +  C02  =  C6H5  •  C02H. 

This  and  the  preceding  methods  are  of  special  interest  from  the 
scientific  point  of  view,  for  the  reason  that  they  clearly  show 
the  relation  between  benzoic  acid,  on  the  one  hand,  and  ben- 
zene and  carbonic  acid,  on  the  other. 

NOTE  FOR  STUDENT. —  Which  of  the  methods  above  given  are  of  gen- 
eral application  for  the  preparation  of  the  acids  of  carbon  ? 

Benzoic  acid  is  prepared  on  the  large  scale:  (1)  from  gum 
benzoin  by  sublimation ;  (2)  from  the  urine  of  horses  and  cows 
by  treating  the  hippuric  acid  with  hydrochloric  acid ;  (3)  from 
toluene,  best,  by  converting  it  into  benzyl  chloride,  and  oxidiz- 
ing this  with  dilute  nitric  acid. 

Experiment  68.  If  the  material  is  obtainable,  evaporate  a  quantity 
of  the  urine  of  horses  or  cows  to  about  one-half  or  one-third  its  volume. 
Add  hydrochloric  acid.  On  cooling,  hippuric  acid  will  be  deposited.  Re- 
crystallize  this  several  times  from  dilute  nitric  acid.  Boil  the  hippuric  acid 


BENZOIC    ACID  323 

for  about  a  quarter  of  an  hour  with  ordinary  concentrated  hydrochloric 
acid.  By  this  means  the  hippuric  acid  is  decomposed,  yielding  glycine 
(amino-acetic  acid)  and  benzoic  acid  :  — 


C9H9N03  +  H20  =  C7H602 

Hippuric  acid  Benzoic  acid 

Glycine 

Benzoic  acid  forms  lustrous  laminae  or  needles,  which  melt 
at  121°.  It  boils  at  250°. 

Experiment  69.  Determine  the  melting-point  of  the  benzoic  acid 
which  you  have  made  from  hippuric  acid.  If  it  is  not  as  stated  above, 
recrystallize  from  water  until  the  melting-point  is  not  changed  by  further 
crystallization.  Those  specimens  which  are  least  pure  can  be  purified  by 
recrystallizing  them  from  dilute  nitric  acid. 

The  acid  is  comparatively  easily  soluble  in  hot  water,  but 
difficultly  soluble  in  cold  water.  It  is  volatile  with  steam. 

Experiment  70.  Put  some  in  a  one-litre  flask,  with  about  700CC  to 
800CC  water.  Connect  with  a  condenser,  and  boil  down  to  about  200CC. 
Neutralize  the  distillate  with  ammonia,  and  evaporate  down  to  a  small 
volume.  Acidify,  when  benzoic  acid  will  be  thrown  down. 

Its  vapor  acts  upon  the  mucous  membrane  of  the  respiratory 
passages,  and  causes  coughing. 
It  sublimes  very  easily. 

Experiment  71.  Put  some  dry  benzoic  acid  in  a  small,  dry  crystal- 
lizing dish,  and  put  the  dish  in  a  sand-bath.  Over  the  mouth  of  the  dish 
put  a  paper  cone  made  from  filter-paper,  arranged  as  shown  in  Fig.  14. 
Heat  with  a  small  flame.  The  benzoic  acid  will  be  deposited  on  the  paper 
in  beautiful  lustrous  needles. 

Or  another  form  of  apparatus,  which  is  useful  for  subliming  small 
quantities  of  substance,  consists,  essentially,  of  two  watch-glasses  which 
are  of  exactly  the  same  size.  The  edges  of  the  glasses  are  ground  to 
secure  a  good  joint  when  they  are  brought  together.  In  using  this  appa- 
ratus, put  the  substance  to  be  sublimed  in  one  of  the  glasses  ;  stretch  a 
round  piece  of  filter-paper  over  it,  and  then  place  the  other  glass  upon  it. 


324 


DERIVATIVES    OF   THE   BENZENE    SERIES 


Clamp  the  glasses  together  by  means  of  a  thin  brass  clamp.     Now  put  the 
glasses  on  a  sand-bath,  and  warm  gently,  when  the  substance  will  slowly 


Fig.  14. 

pass  through  the  paper  and  appear  in  crystals  in  the  upper  watch-glass. 
It  is  well  to  keep  a  small  pad  of  moist  filter-paper  on  the  upper  glass  during 
the  operation. 

When  heated  with  lime,  benzoic  acid  breaks  up  into  benzene 
and  carbon  dioxide  (see  Exp.  53) :  — 

C7H602  =  C6H6  +  CO* 

With  sodium  amalgam,  it  yields  benzyl  alcohol  and  other  re- 
duction-products. With  hydriodic  acid,  it  yields  toluene,  and 
then  hydrogen  addition-products  of  toluene. 

A  great  many  derivatives  of  benzoic  acid  are  known. 

Nearly  all  its  salts  are  soluble  in  water. 


BENZOYL   CYANIDE  325 

Sodium  benzoate  in  small  quantities  is  extensively  used  as  a 
preservative. 

The  ethereal  salts  can  be  made  by  any  of  the  general 
methods  already  described. 

Experiment  72.  To  50s  benzole  acid,  add  100s  absolute  alcohol  and 
10s  concentrated  sulphuric  acid  and  boil  for  3  hours  under  a  return  con- 
denser. Now  add  three  or  four  volumes  of  water,  when  ethyl  benzoate 
will  separate  as  an  oil.  Wash  with  water  and  a  little  sodium  carbonate  ; 
and,  finally,  dry.  Yield  55s  or  90  per  cent  of  the  calculated. 

Benzoyl  chloride,  C6H5.COC1,  and  bromide,  C6H5.COBr, 
are  made  from  benzoic  acid  in  the  same  way  that  acetyl  chlo- 
ride is  made  from  acetic  acid.  On  the  large  scale  the  chloride 
is  made  from  benzoic  aldehyde  by  treating  it  with  chlorine :  — 

C6H5.COH  +  C12=  C6H5.COC1  +  HC1. 

They  are  more  stable  than  the  corresponding  compounds  of 
the  fatty  acids,  but  undergo  the  same  kinds  of  change. 

Benzoyl  chloride  acts  upon  alcohols  and  phenols,  amino  and 
imino  compounds  in  the  same  way  that  acetyl  chloride  does, 
and  forms  benzoyl  compounds :  — 

C6H5.OH  +  C6H5.COC1  =  G6H5.CO.OC6H5  +  HC1. 

The  reaction  is  much  aided  by  the  addition  of  caustic  potash 
(Baumann-Schotten  reaction).  An  example  of  this  is  repre- 
sented thus : — 

C6H5OH+C6H5COCl+NaOH=C6H5.COOC6H5+NaCl+H20. 

The  Baumann-Schotten  reaction  furnishes  a  valuable  method 
for  detecting  hydroxyl,  amino,  and  imino  groups. 

Benzoyl  cyanide,  C6H5 .  CO .  ON,  is  made  by  distilling 
mercuric  cyanide  and  benzoyl  chloride :  — 

2  C6H5 .  COC1  +  Hg(CN)2  =  2  C6H5 .  COCK  +  HgCl2. 


326  DERIVATIVES   OF   THE  BENZENE   SERIES 

The  cyanogen  can  be  converted  into  carboxyl,  and  thus  an  acid 
of  the  formula  C6H5  .  CO  .  C02H  obtained.  This  is  known  as 
benzoyl-formic  acid.  It  is  of  interest,  for  the  reason  that  one  of 
its  derivatives  is  closely  related  to  indigo  (see  Isatine). 

Substitution-Products  of  Benzoic  Acid 

Benzoic  acid  readily  yields  substitution-products  when  treated 
with  the  halogens,  and  with  nitric  and  sulphuric  acids.  The 
products  obtained  by  direct  substitution  belong  mostly  to  the 
meta  series.  Thus,  when  chlorine  acts  upon  benzoic  acid,  the 
main  product  is  meta-chlor-benzoic  acid  ;  nitric  acid  gives  mainly 
metarnitro-benzoic  acid  ;  and  sulphuric  acid  gives  mainly  meta- 
sulpho-benzoic  acid. 

NOTE  FOR  STUDENT.  —  Compare  this  with  the  result  of  the  direct 
action  of  the  same  reagents  on  toluene. 

Substituted  benzoic  acids  can  be  made,  also,  by  oxidizing  the 
corresponding  substituted  toluenes.  Thus,  chlor-toluene  gives 
chlor-benzoic  acid  ;  nitro-toluene  gives  nitro-benzoic  acid,  etc.  :  — 

C6H4C1.CH3      gives  C6H4C1.C02H; 
C6H4(N02)CH3      «      C6H4(N02)C02H. 

The  three  nitro-benzoic  acids  and  the  corresponding  amino- 
benzoic  acids  may  serve  as  examples  of  the  mono-substitution 
products. 


/  f  O  TT\ 

Ortho-nitro-benzoic    acid,     C7H5NO4  (  C6H4  <       2     ].  — 

\          NO2(0)/ 

Ortho-nitro-benzoic  acid  is  formed,  together  with  a  large  quan- 
tity of  the  meta  acid  and  some  of  the  para  acid,  by  treating 
benzoic  acid  with  nitric  acid,  by  oxidizing  ortho-nitro-toluene 
with  potassium  permanganate,  and  by  oxidizing  ortho-nitro- 
cinnamic  acid.  It  crystallizes  in  needles,  melts  at  147°,  and 
has  an  intensely  sweet  taste. 


ANTHRANILIC   ACID  827 

f  O  TT 

Meta-nitro-benzoic  acid,  C6H4  <     _2     ,  is  the  chief  prod- 


uct  of  the  action  of  nitric  acid  on  benzoic  acid.     It  crystallizes 
in  laminae,  or  plates,  and  melts  at  140°  to  141° 

I"*O  TT 

Para-nitro-benzoic  acid,  C6H4<       2    ,  is  prepared  best 


by  oxidizing  para-nitro-toluene.  It  crystallizes  in  laminae, 
melts  at  238°,  and  is  much  less  easily  soluble  in  water  than 
the  ortho  and  meta  acids. 

The  determination  of  the  series  to  which  these  three  acids 
belong  is  effected  by  transforming  them  into  the  amino-acids  ; 
and  these,  through  the  diazo  compounds,  into  the  corresponding 

OTT 

hydroxy-acids  of  the  formula  C6H4<CO  H< 

NOTE  FOR  STUDENT.  —  Give  the  equations  representing  the  action 
involved  in  passing  from  toluene  to  ortho-hydroxy-benzoic  acid  (salicylic 
acid)  by  the  method  above  referred  to. 

In  a  similar  way,  lines  of  connection  can  be  established 
between  the  three  hydroxy-acids  and  the  chlor-,  brom-,  and 
iodo-benzoic  acids.  t 

NOTE  FOR  STUDENT.  —  What  are  the  reactions  ? 

The  three  hydroxy-acids,  on  the  other  hand,  have  been  made 
by  methods  that  connect  them  directly  with  the  three  dibasic 

fT)     TT 

acids  of  benzene,  CeH4  <  CO2H?  which,  in  turn,  have  been  made 
from  the  three  xylenes. 


Ortho-amino-benzoic  acid, 

Anthranilic  acid,  \  ^iai^  W2  V^6Xl4  ^  NH2(0), 

This  acid  is  made  by  reducing  ortho-nitro-benzoic  acid  with 
tin  and  hydrochloric  acid,  and,  on  the  large  scale,  from  phthal- 
imide  by  Hofmann's  reaction  (see  p.  214):  — 


328  DERIVATIVES    OF    THE   BENZENE   SERIES 


C«H4  <  +  2  NaBr  +  CO2  +  H20. 


It  is  also  formed  by  boiling  indigo  with  caustic  potash.  It  has 
already  been  stated  that  indigo  yields  aniline.  Now,  as  ortho- 
amino-benzoic  acid  is  also  obtained,  and  this  breaks  up  easily 
into  aniline  and  carbon  dioxide, 


CeH,  <  =  C6H5NH2  +  C02, 

L>(J2ti. 

it  seems  probable  that  the  aniline  is  a  secondary  product. 

Like  other  amino  acids,  anthranilic  acid  is  probably  an  inner 
salt  and  should,  accordingly,  be  represented  by  the  formula 

f^/~\ 

>.        When  it  is  diazotized  it  yields  an  inner  dia- 


•3 

zonium  salt  of  the  formula  CeH4  <  N2  >.     When  this  is  boiled 

HI 

N 

with  water  it  yields  salicylic  acid :  — 


*  N 
III 

N 

Isatine,  C8H5NO2f  CeH4  <  52  >  CO  J.  — Isatine  is  obtained 

by  the  oxidation  of  indigo,  and  from  ortho-nitro-benzoic  acid 
as  follows :  — 

The  nitro-acid  is  converted  into  the  chloride,  the  chloride 
into  the  cyanide,  and  this  into  the  corresponding  carboxyl 
derivative,  which  is  the  ortho-nitro  derivative  of  benzoyl- 
formic  acid.  The  ortho-nitro-benzoyl-formic  acid  is  then 
reduced  to  the  amino  compound  and  this  loses  water  and  gives 
isatine.  The  changes  are  indicated  thus :  — 


ISATINE  329 

COOH  .COC1  CO.CK 


CO.COOH  CO.COOH      „  „      CO  ^  r  nw 

^C«H*<  C'° 


The  formula  given  for  isatine  represents  it  as  an  anhydride 
of  ortho-ainino-benzoyl-formic  acid.  The  formation  of  anhy- 
drides of  aromatic  acids  is  a  characteristic  of  ortho  compounds. 
Neither  the  meta  nor  para  acids  give  up  water.  We  shall  find 
that  this  fact  is  illustrated  in  the  case  of  the  dibasic  acids,  the 
only  one  that  yields  an  anhydride  being  ortho-phthalic  acid, 

r^ooi-T  r^r\ 

C6H4  <  QOQJJ     >  which  gives  phthalic  anhydride,  C6"H4  <       >O. 

This  ready  formation  of  anhydrides  from  ortho  compounds, 
taken  together  with  the  fact  that  the  meta  and  para  compounds 
do  not  yield  anhydrides,  has  been  regarded  as  an  argument  in 
favor  of  the  view  that  in  the  ortho  compounds  the  two  substi- 
tuting groups  are  actually  nearer  together  than  in  the  meta 
and  para  compounds. 

Isatine  illustrates  the  phenomenon  of  tautomerism  (see  p. 
92).  Towards  some  reagents  it  reacts  as  though  it  contained 
hydroxyl;  towards  others  as  though  it  contained  the  imino 
group  NH,  as  represented  by  the  two  formulas  :  — 

and    C6 

The  first  of  these  formulas  is  known  as  the  lactim,  the  second 
as  the  lactam  formula.  The  evidence  is  in  favor  of  the  lactam 
formula  for  isatine. 

Meta-  and  Para-amino-benzoic  acids  are  made  from  the 
corresponding  nitro  acids  by  reduction. 


330  DERIVATIVES    OF   THE   BENZENE   SERIES 

Hippuric  acid,  benzoyl-amino-acetic  acid, 
C9H9NO3  (C6H5 .  CONH .  CH,CO2H). 

Hippuric  acid,  as  has  already  been  seen  (Exp.  68),  occurs  in 
the  urine  of  herbivorous  animals,  as  the  cow,  horse,  camel,  and 
sheep.  Some  hippuric  acid  is  found  in  human  urine  under 
ordinary  circumstances.  If  benzoic  acid  is  taken  with  the 
food,  it  appears  as  hippuric  acid  in  the  urine,  while  derivatives 
of  benzoic  acid  appear  as  derivatives  of  hippuric  acid. 

Hippuric  acid  can  be  made  synthetically  from  benzoic  acid 
and  acetic  acid : 

1.    By  heating  glycine  with  benzoic  acid  to  160° :  — 


/^rvirvTTi_i_iAAiJ"LJ^  ^  mu        r<TJ    ^  ^H  .  CO  .  06H5       -TT  r\ 

'  •  C0ffi +  H02C  >    Ha  =  CHa  <  C02H  +  H2°- 

Hippuric  acid 

2.   By  heating  benzamide  with  chlor-acetic  acid :  — 


C6H5  .  CO  .  NHH  +  HQ     >  CH2  =         '  >  CH2  +  HC1. 

Hippuric  acid 

3.  By  heating  glycine  with  benzoyl  chloride  :  — 


Hippuric  acid  crystallizes  from  water  in  long,  orthorhombic 
prisms  which  melt  at  187°. 

It  is  decomposed  into  benzoic  acid  and  glycine  by  boiling 
with  alkalies,  and  more  readily  by  boiling  with  dilute  acids 
(Exp.  68):  — 


CH2  <         75°  +  H'0  =  CH2  <  coin  +  C^5  '  C°2H' 


NOTE  FOR  STUDENT.  —  What  relation  does  hippuric  acid  bear  to  ben- 
zamide ?  What  is  the  effect  of  boiling  acid  amides  with  alkalies  ?  Write 
the  equation  for  the  decomposition  of  benzamide,  and  compare  it  with 
that  for  the  decomposition  of  hippuric  acid. 


TOLUIC   ACIDS  331 


Sulpho-benzoic  acids,  C6H4  <  „        __.  —  When  sulphuric 


acid  or  sulphur  trioxide  acts  upon  benzoic  acid  the  principal 
product  is  generally  meta-sulpho-benzoic  acid.  The  ortho-  and 
para-acids  can  be  made  by  oxidizing  ortho-  and  para-toluene- 
sulphonic  acids  :  — 

CH3  COOH 

t6t±4  <  S02OH^    °6tl4  <  S02OIT 

When  the  amide  of  ortho-toluene-sulphonic  acid  is  oxidized 
with  potassium  permanganate  it  gives  the  potassium  salt  of  a 

CO 
compound  of  the  formula,  C6H4  <       >  NH,  which  has  been  called 

oi_/2 

benzoic  sulphinide,  and  on  acidifying,  this  is  precipitated  :  — 

^^3         —^  P  TT    ^   ^^3       ^  P  TT   ^  ^^3 

S02OH  "    °6tl*  <  S02C1^  L^4  <  S02NH2  H 


Benzoic  sulphinide  has  five  hundred  times  the  sweetening 
power  of  cane  sugar,  and  in  consequence  it  has  come  into  ex- 
tensive use  as  a  sweetening  agent.  In  commerce  it  is  known 
as  saccharin.  It  is  a  crystallized  substance  rather  difficultly 
soluble  in  water.  It  is  soluble  in  acetone,  and  crystallizes 
beautifully  from  this. 

Toluic  acids,  C8H8O2.  —  There  are  four  acids  of  this  formula 
known  ;  viz.,  the  three  carboxyl  derivatives  of  toluene  in  which 

C^  PT 

the  carboxyl  enters  into  the  benzene  ring,  C6H4<      3  ,  and  an 

C/  w2-H- 

acid  obtained  from  toluene  by  replacing  a  hydrogen  of  the 
methyl   by  carboxyl,  thus,  C6H5  .  CH2  .  C02H.       Ortho-,  meta-, 

OTT 

and  para-toluic  acids,  C6H4<C03H,  are  made  by  oxidizing  the 
corresponding  xylenes  with  nitric  acid  :  — 

+  3  0  =  C6H4  <    °     +  H20. 


332  DERIVATIVES    OF   THE   BENZENE   SERIES 

They,  as  well  as  their  derivatives,  of  which  many  are  known, 
have  been  studied  carefully.  The  substituted  toluic  acids  can 
be  made  either  by  treating  the  acids  with  strong  reagents  or 
by  oxidizing  substituted  xylenes  :  — 


C6H3(N02)  <         +  3  0  =  C6H3(N02)  <  $g    +  H20. 

Nitro-xylene  Nitro-toluic  acid 


benzoic  acid  may  be  regarded  as  phenyl-formic  acid,  so  a-toluic 
acid  may  be  regarded  as  phenyl-acetic  acid.  It  is  obtained  by  re- 
ducing mandelic  or  phenyl-gly  colic  acid,  C6H5.  CH(OH)  .  C02H, 
which  is  formed  when  amygdalin  is  treated  with  hydrochloric 
acid.  It  is  prepared  from  toluene  by  converting  this  into 
benzyl  chloride,  from  which  the  cyanide  is  made  by  boiling  with 
potassium  cyanide.  The  cyanide  is  then  treated  with  an  alkali 
and  yields  the  acid  :  — 

C6H5.CH3       +  C12       =C6H5.CH2C1          +HC1; 

Boiling  toluene  Benzyl  chloride 


C6H5  .  CH2C1   +  KCN  =  C6H5  .  CH2CN       +  KC1  ; 

Benzyl  cyanide 

C6H5  .  CH2CN  +  2  H20  =  C6H5  .  CH2  .  C02H  +  NH3. 

a-Toluic  acid 

The  acid  crystallizes  in  thin  laminae  ;  and  melts  at  76.5°. 

NOTE  FOR  STUDENT.  —  What  would  you  expect  a-toluic  acid  to  yield 
when  oxidized  ?  (See  p.  270.)  What  would  you  expect  it  to  yield  when 
distilled  with  lime?  What  would  you  expect  the  three  toluic  acids, 

c*  w 
CeH^  <       3    ,  to  yield  by  oxidation,  and  when  distilled  with  lime  ?     (See 

C/C^fl 

p.  324.) 

Oxindol,  C8H7No(c6H4<^:E2>Co).  —  Oxindol  is  obtained 

by  reduction  of  isatine  (see  p.  328)  ;  and  also  from  ortho-amino- 
a-toluic  acid  by  loss  of  water,  in  the  same  way  that  isatine 


HYDRO-CINNAMIC   ACID  333 

is  formed  from  ortho-amino-benzoyl-formic  acid.  When  a-toluic 
acid  is  treated  with  nitric  acid,  the  para-  and  ortho-nitro  acids 
are  formed.  The  latter  is  reduced  by  means  of  tin  and  hydro- 
chloric acid,  when  oxindol  is  at  once  obtained  :  — 


CH2 
NH 

Ortho-amino-a-toluic  acid  Oxindol 


Mesitylenic    acid,    C9H10O2c6H3<2     —  This  acid 


has  already  been  referred  to  as  the  first  product  of  oxidation 
of  mesitylene.  It  is  the  only  monobasic  acid  that  has  been 
obtained  from  mesitylene;  and,  according  to  the  accepted 
hypothesis,  it  is  the  only  one  possible.  By  distillation  with 
lime,  it  yields  meta-xylene.  Further  oxidation  converts  it 
into  uvitic  and  trimesitic  acids  (see  p.  270). 

NOTE  FOR  STUDENT.  —  Of  what  special  significance  is  the  formation  of 
meta-xylene  from  mesitylenic  acid  ? 

Hydro-cinnamic  acid,   )  r  TT  n  ,r  -p.   ^-p.    ^TT    rr»  -m 

-I-M  1  •  -J        V  OnXlin^CUfiXlr.Oxlo.  UHo  .  OOoM). 

Phenyl-propiomc  acid,  j     9 

—  Hydro-cinnamic  or  /3-phenyl-propionic  acid  is  obtained  by 
treating  cinnamic  acid  with  nascent  hydrogen  :  — 

C6H5  .  CH  :  CH  .  C02H  +  H2  =  C6H5  .  CH2  .  CH2  .  C02H. 

Cinnamic  acid,  Hydro-cinnamic  acid, 

/3-Phenyl-acrylic  acid  /3-Phenyl-propionic  acid 

It  is  also  made  by  starting  with  ethyl-benzene,  C6H5  .  C2H6, 
and  carrying  out  the  same  reactions  that  are  necessary  to 
transform  toluene  into  a-toluic  acid  (see  p.  332).  It  is  a 
product  of  the  decay  of  several  animal  substances,  such  as 
albumin,  fibrin,  brain,  etc.  It  crystallizes  from  water,  in  long 
needles,  which  melt  at  48°.  It  yields  benzoic  acid  when  oxi- 
dized. 


834  DERIVATIVES   OF   THE  BENZENE  SERIES 


Ortho-amino-hydro-   )  r«  TT  ^-        2  •          •        2 

•  J  f      ^'6-E14  ^   -XTTT  •    -     *  -"J-IS 

cinnamic  acid,        j  -NH2(o) 

acid  is  prepared  from  hydro-cinnamic  acid  in  the  same  way 
that  ortho-amino-a-toluic  acid  is  made  from  a-toluic  acid.  It 
is  not  obtained  in  the  free  state;  but,  like  the  ortho-amino 
derivatives  of  benzoyl-formic  and  of  a-toluic  acids,  it  loses 
water,  and  forms  the  anhydride. 

C  H 

Hydro-carbostyril,  C6H4  <    *    4^  C  .  OH.  —  Hydro-carbo- 

styril  is  made  by  treating  ortho-nitro-hydro-cinnamic  acid  with 
tin  and  hydrochloric  acid.  It  is  a  solid  that  crystallizes  in 
prisms,  melting  at  160°.  It  is  interesting  chiefly  for  the  reason 
that  it  is  closely  related  to  the  important  compound  quinoline 
(which  see).  When  treated  with  phosphorus  pentachloride, 
hydro-carbostyril  is  converted  into  di-chlor-quinoline.  The 
significance  of  this  reaction  will  appear  later. 


DIBASIC  ACIDS,  CnH2n_1004 

The  simplest  acids  of  this  group  are  the  three  phthalic  acids, 
which  are  the  di-carboxyl  derivatives  of  benzene,  belonging  to 
the  ortho,  meta,  and  para  series. 

Phthalic  acid,  \  m  nfrtr  ^  CO2 

Ortho-phthalicacid,  |C8H6°{C6H4 
acid  was  the  first  of  the  three  acids  of  this  composition  dis- 
covered; and,  as  it  was  obtained  from  naphthalene,  it  was 
named  phthalic  acid.  It  is  manufactured  on  the  large  scale 
by  oxidizing  naphthalene  by  means  of  concentrated  sulphuric 
acid  in  the  presence  of  a  little  mercuric  sulphate  at  a  tem- 
perature of  220°-300°.  It  can  further  be  formed  from  alizarin 

PTT 

and  purpurin;   and  from  ortho-toluic  acid,  C6H4<cQ3H    '  ^ 
oxidation  with  potassium  permanganate. 


ISOPHTHALIC    ACID  335 

Experiment  73.  Mix  5s  naphthalene,  is  mercury,  and  800s  com- 
mercial fuming  sulphuric  acid  in  a  retort  of  about  300CC  capacity  ;  con- 
nect with  a  receiver  cooled  with  water,  heat  slowly  nearly  to  boiling. 
Soon  a  white  sublimate  of  phthalic  anhydride  will  appear  in  the  upper 
part  and  in  the  neck  of  the  retort.  When  nothing  more  passes  over 
pour  the  liquid  from  the  solid  contained  in  the  receiver,  and  crystallize 
from  water.  The  phthalic  acid  thus  obtained  will  be  needed  for  other 
experiments. 

Phthalic  acid  forms  orthorhombic  crystals,  which  melt  at 
213°  or  lower,  according  to  circumstances,  for,  when  heated,  it 
breaks  up  gradually,  even  below  the  melting-point,  into  water 
and  the  anhydride  which  melts  at  128°.  Distilled  with  lime, 
it  yields  benzene  ;  though,  by  selecting  the  right  proportions, 
benzoic  acid  can  be  obtained  :  — 


PO  TT 
(2)  C6H<  <  JJJg  =  C6H5  .  C02H  +  C<V 

Phthalic  acid  is  oxidized  by  chromic  acid  to  carbon  dioxide 
and  water.  Hence  it  cannot  be  made  from  ortho-xylene  by 
oxidation  with  chromic  acid.  By  boiling  ortho-xylene  with 

|"1  TT 

nitric  acid,  however,  it  yields  ortho-toluic  acid,  C6H4<      8 


and  this  can  be  oxidized  to  phthalic  acid  by  treatment  with 
potassium  permanganate. 

CO 

Phthalic  anhydride,  C6H4  <        >  O,  is  formed  by  heat- 


ing phthalic  acid.  It  forms  long  needles,  which  melt  at  128°. 
Heated  with  phenols,  it  forms  the  compounds  known  asphthal- 
eins  (which  see). 

Isophthalic  acid,       1  r«  TT  ^  CJO2H        .  , 

Meta-phthalicacid,     °H<  1S  f°rmed 


dizing  either  meta-xylene   or   meta-toluic  acid  with  chromic 


336  DERIVATIVES   OF   THE   BENZENE   SERIES 

acid  ;  by  distilling  meta-benzene-disulphonic  acid  with  potas- 
sium cyanide,  and  boiling  the  resulting  dicyanide  with  an 
alkali. 

NOTE  FOR  STUDENT.  —  Write  the  equations  representing  the  action 
involved  in  passing  from  meta-benzene-disulphonic  acid  to  isophthalic 
acid.  Into  which  dihydroxy-benzene  is  this  same  disulphonic  acid  con- 
verted by  melting  it  with  caustic  potash  ? 

The  acid  is  formed,  further,  by  heating  the  potassium  salt 
of  meta-sulpho-benzoic  acid  with  sodium  formate  :  — 


a  =  C6H4  <  +  HKSO 


Potassium  sulpho-  Potassium  sodium 

benzoate  isophthalate 

.  This  reaction  is  of  importance,  for  the  reason  that  the  same 
sulpho-benzoic  acid,  which  is  thus  converted  into  isophthalic 
acid,  can  also  be  converted  into  one  of  the  three  hydroxy- 
benzoic  acids;  and  thus  connection  is  established  between 
the  latter  and  isophthalic  acid  and  meta-xylene. 

Isophthalic  acid  crystallizes  in  fine  needles  from  water.     It 
melts  above  300°,  and  is  not  converted  into  an  anhydride. 


Terephthahc  acid,  )  r«  TT  /  CO2H  rp  ,  ,  ,.  . , 
•DO,*  r^+v,ov^  -A  f  C6H4 <  r.^  XT  • — Terephthahc  acid 
Fara-pntnalic  acid,  )  COaH^) 

is  formed  by  oxidation  of  the  oil  of  turpentine,1  cymene,  para- 
xylene,  and  para-toluic  acid ;  by  heating  a  mixture  of  potas- 
sium para-sulpho-benzoate  and  sodium  formate :  — 

PO  TT  f?(~\  TT 

f^    TT  -  V>VJ*V  yj        /-MX-^    -».-r  x^    -r-r-  V/W^XV 

O6±14  <  ar^       .      +  M  . 


Potassium  para-  Potassium  sodium 

sulpho-benzoate  terephthalate 

Para-sulpho-benzoic  acid  is  converted  into  one  of  the  three 
hydroxy-benzoic  acids  by  caustic  potash.     In  the  para  as  well 

»  The  prefix  tere  is  derived  from  the  Latin  terebinthinus,  turpentine. 


PHENOL-ACIDS    OF    THE    BENZENE    SERIES  337 

as  the  meta  series,  the  lines  of  connection  indicated  below  have 
been  established  :  — 

CH3 


Terephthalic  acid  is  a  solid  that  is  practically  insoluble  in 
water.  It  sublimes  without  melting  and,  like  isophthalic  acid, 
yields  no  anhydride. 

HEXABASIC  ACID 

Mellitic  acid,  C12H6O12[C6(CO2H)6].  —  This  acid  occurs  in 
nature  in  the  form  of  the  aluminium  salt,  as  the  mineral 
honey-stone  or  mellite.  The  mineral  is  rare,  and  is  found  in 
beds  of  lignite.  Mellitic  acid  has  been  made  by  direct  oxida- 
tion of  carbon  with  potassium  permanganate,  and  by  oxidation 
of  hexa-methyl-benzene,  C6(CH3)6.  By  ignition  with  soda-lime 
it  is  converted  into  benzene  and  carbon  dioxide  :  — 

C6(C02H)6  =  C6H6  +  6  C02. 

PHENOL-ACIDS,  OR  HYDROXY-ACIDS  OF  THE  BENZENE  SERIES 

It  will  be  remembered  that  the  alcohol  acids  or  hydroxy- 
acids  of  the  paraffin  series  form  an  important  class,  including 
such  compounds  as  glycolic,  lactic,  malic,  tartaric,  and  citric 
acids.  The  peculiarity  of  these  compounds  is  their  double 
character.  They  are  at  the  same  time  alcohols  and  acids, 
though  the  acid  properties  are  more  prominent  than  the  alco- 
holic. The  hydroxy-acids  of  the  benzene  series  bear  the  same 
relations  to  the  benzene  hydrocarbons  that  the  hydroxy-acids 


338  DERIVATIVES    OF   THE    BENZENE   SERIES 

already  studied  bear  to  the  paraffins.     The  simplest  are  those 
which  contain  one  hydroxyl  and   one   car  boxy  1   in   benzene, 

O  H 

having  the  formula  C6H4<CO  H« 

MONO-HYDROXY-BENZOIC    AdDS,    C7H603 

Salicylic  acid,  1     __     OH 


Ortho-hydroxy-benzoic  acid,  J  CO2H  (*)  '  "   oaiicy  li 

acid  is  found  in  the  form  of  an  ethereal  salt  of  methyl,  in  the 
oil  of  wintergreen,  prepared  from  the  blossoms  of  Gaultlieria 
procumbens.  It  is  formed  in  a  number  of  ways,  among  which 
the  following  should  be  specially  mentioned  :  — 

1.  By  converting  ortho-amino-benzoic    acid  into  the  diazo 
compound,  and  boiling  with  water  (see  p.  328). 

NOTE  FOR  STUDENT.  —  Give  the  equations  representing  the  reactions. 

2.  By  fusing  a  salt  of  ortho-sulpho-benzoic  acid  with  caustic 
potash. 

NOTE  FOR  STUDENT.  —  Write  the  equation. 

3.  By  treating  sodium  phenolate  with  carbon  dioxide.     The 
sodium  salt  is  first  saturated  with  carbon  dioxide  under  press- 
ure in  closed  vessels.     This  gives  sodium  phenyl  carbonate, 
C6H5.O.C02^Ta.     By  heating  this  to  120-130°  under  pressure 
it  is  converted  into  sodium  salicylate  :  — 

C6H5  .  0  .  C02Na  =  C6H4  <  £H 

4.  By  heating  phenol  with  tetra-chlor-methane  and  an  alco- 
holic solution  of  potassium  hydroxide  :  — 


C6H5  .  OH  +  CC14  +  6  KOH  =  C6H4<  +  4  KC1  +  4  H20. 

OU2rv 

5.    By   saponifying  the   methyl   salicylate  found  in  oil  of 
wintergreen  :  — 

OTT  OTT 

COaCH3  +  KOH  =  C«H< 


SALICYLIC   ACID 


339 


Experiment  74.  Boil  10CC  to  15CC  oil  of  wintergreen  with  moder- 
ately strong  caustic  potash  in  a  flask  connected  with  an  inverted  con- 
denser. When  it  is  dissolved,  acidify  with  hydrochloric  acid.  Filter  off 
the  salicylic  acid  which  separates,  and  recrystallize  from  water. 

Experiment  75.  Dissolve  80s  sodium  hydroxide  and  40s  phenol  in 
130CC  water  in  a  litre  flask,  arranged  as  in  Fig.  15.  If  the  mixture  is  cool, 
heat  to  50-60°,  and  remove  the  flame.  Slowly  add  60s  chloroform,  shak- 
ing the  mixture  for  several  minutes  after  each  addition.  The  mixture 
gradually  becomes  dark  colored.  An  hour  or  more  may  be  required 


Fig.  15. 

to  complete  the  addition  of  all  the  chloroform.  When  the  action  is  over, 
boil  for  an  hour,  and  then  distil  off  the  excess  of  chloroform  on  the  water- 
bath.  Acidify  with  dilute  hydrochloric  acid,  when  a  thick  reddish  brown 
oil  comes  down.  Distil  in  steam  as  in  Exp.  66,  until  the  distillate  no 
longer  appears  in  milky  drops.  A  light-colored  oil  consisting  of  salicylic 
aldehyde  and  phenol  settles  in  the  receiver.  Decant  the  supernatant 
water.  Extract  with  ether,  and  concentrate  the  extract  by  evaporation 
in  a  water-bath.  To  the  concentrated  extract  add  a  saturated  solution 
of  mono-sodium  sulphite  (freshly  prepared  by  dissolving  40s  sodium 


340  DERIVATIVES    OF    THE   BENZENE   SERIES 

sulphite  in  75CC  hot  water,  cooling  the  solution,  and  saturating  with 
sulphur  dioxide).  Shake  the  mixture  8  or  10  times,  2  or  3  minutes  at  a 
time,  for  half  an  hour  ;  then  allow  it  to  stand  for  several  hours.  The 
aldehyde  unites  with  the  sulphite,  forming  small,  glistening,  white 
crystals,  while  the  phenol  remains  in  solution  in  the  ether.  Filter  with 
the  aid  of  a  pump,  and  wash  the  crystals  with  alcohol.  Then  treat  the 
crystals  on  the  water-bath  with  hydrochloric  acid,  when  salicylic  alde- 
hyde is  thrown  down.  Extract  completely  with  ether,  separate  the  two 
solutions,  and  evaporate  the  ether. 

In  an  iron  or  silver  dish,  melt  25s  caustic  potash  ;  remove  the  lamp  ; 
and  add  the  salicylic  aldehyde  drop  by  drop,  stirring  constantly.  The 
potassium  salt  of  salicylic  acid  is  thus  formed.  After  the  mass  is  cooled, 
dissolve  in  water,  and  precipitate  the  salicylic  acid  with  dilute  hydro- 
chloric acid.  Filter,  wash  with  cold  water,  and  purify  by  recrystallizing 
from  water. 

The  action  of  chloroform  on  phenol  in  the  presence  of  caustic 
soda  is  analogous  to  that  of  tetra-chlor-methane.  It  will  be 
understood  with  the  aid  of  the  following  equations:  — 

OTT 

(1)  C6H5  .  OH  +  CHC13  =  C6H4  <  £HC]^  +  HC1; 

(2)  C6H42 

OH  OTT 

(3)  C6H4  <  =  C6H4  <  +  H20. 


This  reaction  is  of  general  application  to  phenols,  and  affords 
a  very  convenient  method  for  the  preparation  of  the  phenol- 
aldehydes  and  from  these  the  acids. 

Salicylic  acid  crystallizes  from  hot  water  in  fine  needles.  It 
melts  at  159°. 

When  heated  with  soda-lime,  it  breaks  up  into  phenol  and 
carbon  dioxide  :  — 


C6H4  <  ~        =  C6H5  .  OH  +  C02. 
Heated  alone  it  gives  phenyl  salicylate  (salol)  and  xanthone:  — 


PHENYL  SALICYLATE  341 

(1) 


Phenyl  salicylate  (salol) 

(2) 


Xanthone 

With  ferric  chloride,  its  aqueous  solution  gives  a  characteristic 
dark  violet-blue  color.  Free  salicylic  acid  is  antiseptic,  pre- 
venting decay  and  fermentation.  It  is  therefore  used  for  pre- 
serving foods.  It  is  also  used  extensively  in  medicine, 
especially  in  rheumatism. 

Acetylsalicylic   add   is   used   in   medicine  under   the   name 
aspirin. 

OTT 

Salicylic  acid  forms  salts  of  the  general  formula  C6H4  <  co  M  ' 

and,  with  the  alkalies,  compounds,  in  which  both  the  phenol 
hydrogen  and  the  acid  hydrogen  are  replaced  by  metals,  as 

C6H4<^  The  basic  calcium  salt,  C6H4<nn  >Ca  +  H20,  is 

UUgJv  t^Ua 

very  difficultly  soluble  in  water,  and  is  converted  by  carbon 
dioxide  into  the  salt  (C6H4<CO  )  Ca-  Salicylic  acid  forms 

OTT 

ethereal  salts  of  the  general  formula  C6H4<CO  R,  of  which 

OTT 

methyl  salicylate,  C6H4<C()  CH  ,  is  the  best-known  example. 

OT? 

It  forms,  also,  ether-acids  of  the  general  formula  C6H4<CO  H; 

OT? 

and,  finally,  compounds  of  the  general  formula  C6H4<CO  R* 


Phenyl   salicylate   (salol),   C6H4  <  _,  __  .  —  This    is 


formed  when  salicylic  acid  is  heated  alone  to  200-220°,  and 
when  salicylic  acid,  phenol,  and  phosphorus  oxychloride  are 
heated  together.  It  is  a  solid  that  melts  at  43°.  It  is  exten- 
sively used  as  an  antiseptic. 


342  DERIVATIVES    OF   THE   BENZENE   SERIES 

That  salicylic  acid  belongs  to  the  ortho  series  is  clear  from 
the  following  facts  :  — 

Ortho-toluene-sulphonic  acid  has  been  converted  into  ortho- 
sulpho-benzoic  acid,  and  this  into  salicylic  acid.  Further,  the 
same  toluene-sulphonic  acid  has  been  converted  into  ortho- 
toluic  acid,  which,  by  oxidation,  yields  phthalic  acid. 


(1)    OA<M      +30     =  CeH4<  +  H20; 

Ortho-toluene-sulphonic  Ortho-sulpho-benzoic 

acid  acid 


(2)     C6H4<  +KOH  =  C6H4<  +K2803; 

k<J3K(o)  U±l(o) 

Potassium  salicylate 


(3)    C6H4<~3  +  KCN  =  C6H4<3  +  K2S03; 

vJM  (0) 


Ortho-toluic  acid 

(5)    C6H4<J^3  +30     =  C6H4<°°2**        +H20. 

L,U2-tl(0)  UU2rl(o) 

Phthalic  acid 


Oxybenzoic   acid, 

Meta-hydroxy-benzoic   acid,  CO2H(m)* 

acid  is  made  from  meta-amino-benzoic  and  meta-sulpho-benzoic 
acid  by  the  usual  reactions. 

It  crystallizes  from  water  in  needles  united  to  form  wart- 
like-looking  masses.  It  gives  no  color  with  ferric  chloride. 
Its  connection  with  meta-phthalic  (isophthalic)  acid  and  meta- 
xylene  is  shown  by  means  of  the  transformations  tabulated  on 
p.  337;  that  is  to  say,  the  same  sulpho-benzoic  acid  which,  by 
fusing  with  caustic  potash,  yields  oxybenzoic  acid,  by  fusing 
with  sodium  formate  yields  isophthalic  acid.  Therefore  oxy- 
benzoic acid  is  a  rneta  compound. 


DI-HYDROXY-BENZOIC   ACIDS  343 


Para-oxybenzoic  acid,  \  C  H  <  4-  H  O  - 

Para-hydroxy-benzoic   acid,  j      6    '  ^ 


Para-oxybenzoic  acid  is  formed  from  the  corresponding  amino- 
and  sulpho-benzoic  acids  ;  by  treating  various  resins  with 
caustic  potash  ;  from  anisic  acid  (see  below),  by  heating  with 
hydriodic  acid;  by  heating  potassium  phenolate  in  a  current 
of  carbon  dioxide  to  220°. 

NOTE  FOR  STUDENT.  —  Notice  the  fact  that,  while  sodium  phenolate, 
when  heated  in  a  current  of  carbon  dioxide,  yields  salicylic  acid,  potas- 
sium phenolate,  under  the  same  circumstances,  yields  para-oxybenzoic 
acid. 

Its  aldehyde  is  formed,  together  with  salicylic  aldehyde,  by 
treating  phenol  with  chloroform  and  caustic  soda  (see  Exp.  75). 

The  reasons  for  regarding  para-oxybenzoic  acid  as  a  member 
of  the  para  series  are  similar  to  those  which  show  that  oxy  ben- 
zoic  acid  is  a  meta  compound.  The  same  sulpho-benzoic  acid 
that  yields  para-oxybenzoic  acid  also  yields  terephthalic  acid. 

Anisic  acid,  1  r  TT  ^  OCHs 

Para-methoxy-benzoic  *  acid,  }  °6±±4  s  CO2H   ' 

OCH 

acid  is   formed  by  the  oxidation  of  anethol,  cfiH4  <  ~  ^  3,  a 

^3*15 

phenol  ether  contained  in  anise  oil.  It  is  made  by  heating 
para-oxybenzoic  acid  with  caustic  potash  and  methyl  iodide 
and  saponifying  the  di-methyl  ether  thus  formed.  As  the 
formula  indicates,  it  is  the  methyl  ether  of  para-oxybenzoic 
acid.  As  will  be  seen,  it  is  isomeric  with  methyl  salicylate. 
By  boiling  with  caustic  alkali  the  latter  is  saponified,  while 
anisic  acid  is  not.  When  anisic  acid  is  distilled  with  lime, 
anisol  is  formed. 

Dl-HYDROXY-BENZOIC    AdDS,    C7H604 

Protocatechuic  acid,  C6H3  {  2,  is  a  frequent  product 


1  r  TT  ^  s  *    •  - 

,  }  °±±  s  '  ~~  Am 


1  Methoxy  is  derived  from  methotcyl,  the  name  given  to  the  ether  group,  OCH3.     In  a 
similar  way  OC2H6  is  called  ethoxyl;  OCCH8,  phenoxyl,  etc. 


344  DERIVATIVES   OF  THE  BENZENE  SEKIES 

of  the  fusion  of  organic  substances  with  caustic  potash.  Thus, 
the  following  substances,  among  others,  yield  it:  oil  of  cloves, 
piperic  acid,  catechin,  gum  benzoin,  asafoetida,  vanillin,  etc. 
It  is  made  from  sulpho-oxybenzoic  acid,  and  from  sulpho-para- 
oxybenzoic  acids  by  fusing  with  caustic  potash. 

NOTE  FOR  STUDENT.  —  What  analogy  is  there  between  the  fact  that 
protocatechuic  acid  is  formed  from  sulpho-oxybenzoic  acid  and  from 
sulpho-para-oxybenzoic  acid,  and  the  fact  that  pseudocumene  is  formed 
from  brom-meta-xylene  and  from  brom-para-xylene  ?  What  conclusion 
may  be  drawn  regarding  the  relations  of  the  two  hydroxyl  groups,  and 
the  carboxyl  in  protocatechuic  acid  ? 

By  distillation  with  lime,  protocatechuic  acid  breaks  up  into 
pyrocatechol  and  carbon  dioxide  :  — 

rOH 
C6HJOH     = 

I   HCi  TT 
V.  ^U±l 


Pyrocatechol 


Vanillic   acid,   C6H3<  OH    ,   is  formed  by   oxidation  of 
(  CO2H 

vanillin,  which  is  the  corresponding  aldehyde.     It  is  the  mono- 
methyl  ether  of  protocatechuic  acid. 

/          (OCH3\ 

Vanillin,  CJEI8O8(  C6H3  1  OH      ,  is  the  active  constituent 
t 


of  the  vanilla  bean.    It  is  made  artificially  by  treating  the 

or1  I 
npr 


or1  IT 
ether,  guaiacol,  c6H4<npr  3,  with  chloroform  and  caustic  soda. 


rCHO 
Piperonal,  C6H3j  O>CH.  —  This  is  formed  by  oxidizing 

piperic  acid,  which  is  itself  a  product  of  the  decomposition  of 
piperine,   a  complex   compound   that   is    found  in   different 


GALLIC   ACID  345 

varieties  of  pepper.  Piperonal  is  the  methylene  ether  of 
protocatechuic  aldehyde.  It  can  be  made  artificially,  and  is 
used  in  perfumery  under  the  name  lieliotropine.  The  relations 
between  protocatechuic  aldehyde,  vanillin,  and  piperonal  are 
shown  by  the  following  formulas  :  — 

/  CHO  (1)  (  CHO  (1) 

C6HUOH    (3)  C6H3JOCH3(3) 

(OH    (4)  (OH      (4) 

Protocatechuic  Vanillin 

aldehyde 


TRI-HYDROXY-BENZOIC  ACIDS,  C7H605 
Gallic  acid,  C7HfiO.+H2oc(iH2<I3  +  H2o.—  Gallic 


) 

acid  occurs  in  nutgalls,  sumach,  Chinese  tea,  and  in  many 
other  plants.  It  is  formed  by  boiling  tannin  or  tannic  acid 
with  dilute  sulphuric  acid;  by  melting  brom-protocatechuic 
acid  with  caustic  potash:  — 

C6H2  j  (OH),  +  KOH  =  C6H2  <  f9H)s  +  KBr. 
\  C02H  '°2H 

Brom-protocatechuic  Gallic  acid 

acid 

It  is  best  prepared  from  gall  nuts  by  hydrolysis  of  the 
tannin  contained  in  them. 

Gallic  acid  is  difficultly  soluble  in  cold  water,  easily  in  hot 
water,  alcohol,  and  ether.  Its  solution  gives,  with  a  little 
ferric  chloride  solution,  a  blue-black  precipitate,  which  dis- 
solves in  excess  of  ferric  chloride,  forming  a  dark  green 
solution.  It  readily  reduces  gold  and  silver  salts  in  solution. 
When  distilled,  it  yields  pyrogallol  (pyrogallic  acid)  and 
carbon  dioxide:  — 


C6H2  <          3  =  C6H3(OH)3  +C02. 


346  DERIVATIVES    OF   THE   BENZENE   SERIES 

Tannic  acid,  tannin,  Ci4H10O9  +  2  H2O.  —  This  substance 
occurs  in  gall  nuts,  from  which  it  is  extracted  in  large  quan- 
tities. It  is  an  amorphous  powder.  It  is  markedly  astringent. 
It  is  soluble  in  water,  the  solution  giving,  with  ferric  chloride,  a 
dark  blue-black  color.  Tannin  is  used  extensively  in  medicine, 
in  dyeing,  and  in  the  manufacture  of  ink  and  leather  (tanning). 
It  combines  with  gelatin,  forming  an  insoluble  substance.  Its 
relation  to  gallic  acid  is  indicated  by  the  following  equation  :  — 

2  0^05  =  0,411,00,  +  H20. 

Gallic  acid  Tannin 


KETONES  AND  ALLIED  DERIVATIVES  OF  THE  BENZENE  SERIES 

The  ketones  of  the  benzene  series  are  strictly  analogous  to 
those  of  the  paraffin  series,  and  they  are  made  in  the  same 
way.  Acetone  is  made  by  distilling  calcium  acetate  : 


CH..COJO          !  _CH3 

CHJ  co  o  >     :  -  OH,  >  ° ' +  Ca°°3- 


L3i 

Acetone 


So,  also,  benzophenone  or  diphenyl-ketone  is  made  by  distill- 
ing calcium  benzoate :  — 


C6H5.CO;0          |_C,H. 
C.H.i'CO^     i~CJ$, 

Benzophenone 

Further,  by  distilling  mixtures  of  the  salts  of  two  fatty  acids, 
mixed  ketones  are  obtained :  — 

CH3  .  COjOMj        _  CH3 

C2H5.!COqMi        -C2H5>     f**"^ 

Ethyl-methyl 
ketone 

And,  similarly,  mixed  ketones  containing  one  residue  of  a 
benzene  hydrocarbon  and  one  of  a  paraffin,  or  two  different 
residues  of  benzene  hydrocarbons,  can  be  obtained  thus :  — 


QUINONES  347 

C6H5.COOM          c6H 

CH3.COOM          =CH3 


C6H5.COOM 


Phenyl-methyl  ketone, 
Acetophenone 


Phenyl-tolyl-ketone 

Interesting  results  have  been  reached  through  a  study  of  the 
oximes  of  the  aromatic  ketones.  It  has  been  shown  that  while 
the  symmetrical  ketones,  like  benzophenone,  C6H5.CO.C6H5, 
give  but  one  oxime,  some  of  the  unsymmetrical  ketones,  like 
phenyl-tolyl-ketone,  C6H5.CO.C6H4.CH3,  give  two.  This  is 
quite  in  accordance  with  the  views  already  set  forth  in  regard  to 
the  stereochemistry  of  nitrogen  compounds  (see  Benzaldoxime, 
page  320).  In  the  terms  of  stereochemistry  the  two  formulas 

CgHg  .  C  .  C6H5  C6H5  .  C  .  CgTIg 

II  and  || 

HO.N  N.OH 

are  identical,  so  that  a  symmetrical  ketone  can  give  but  one 
oxime.     On  the  other  hand  the  formulas 


s  •  C  .  C6H4  .  CH3  C6H5  .  C  .  C6H4  .  CH3 

II  and  || 

HO.N  N.OH 

are  different,  so  that  an  unsymmetrical  ketone  can  give  two 
oximes. 

QUINONES 

The  quinones  are  peculiar  compounds  which  in  some  ways  are 
allied  to  the  ketones.  The  simplest  example  of  the  class,  and 
the  one  best  known,  is  called  quinone.  Its  formula  is  C6H402, 
and  it  therefore  appears  to  be  benzene  in  which  two  hydrogen 
atoms  are  replaced  by  two  oxygen  atoms.  All  quinones  bear 
this  relation  to  the  hydrocarbons,  of  which  they  may  be  regarded 
as  derivatives. 


348  DERIVATIVES    OF   THE   BENZENE   SERIES 

Quinone,  C6H4O2,  is  formed  by  the  oxidation  of  quinic  acid, 
hydroquinol,  para-diainino-benzene,  and  some  other  benzene 
derivatives  in  which  two  substituting  groups  occupy  the  para 
position  relatively  to  each  other. 

It  is  usually  made  by  oxidizing  aniline  with  sodium  bi- 
chromate and  sulphuric  acid.  In  the  laboratory  it  is  most 
convenient  to  make  it  by  oxidizing  hydroquinol. 

It  forms  long,  yellow  prisms ;  sublimes  in  golden-yellow 
needles ;  is  volatile  with  steam ;  and  has  a  peculiar  penetrating 
odor. 

Sulphurous  acid  reduces  quinone  to  hydroquinol :  — 

C6H402  +  H2S03  +  H80  =  C6H4(OH)2  +  H2S04. 

The  easy  transformation  of  hydroquinol  into  quinone,  and 
the  opposite  transformation  of  quinone  into  hydroquinol,  as 
well  as  the  formation  of  quinone  from  other  para  compounds, 
force  us  to  the  conclusion  that  the  oxygen  atoms  in  quinone 
are  in  the  para  position  relatively  to  each  other.  Quinone 
appears,  therefore,  as  benzene  containing  two  oxygen  atoms  in 
the  para  position  as  represented  in  the  formula:  — 


As  quinone  forms  a  monoxime,  C6H40(NOH),  and  a  dioxime, 
C6H4(NOH)2,  and  takes  up  four  atoms  of  bromine  and  of 
chlorine,  it  is  generally  regarded  as  a  di-ketone  of  the  formula  — 

CO 

CH 


CH 
CO 


ORTHO-BENZOQUINONE 


349 


According  to  this  view  quinone  is  not,  strictly  speaking,  a 
derivative  of  benzene,  but  is  derived  from  dihydrobenzene :  — 

CH2 
HC/NCH 

HcijCH 
CH2 

If  the  di-ketone  formula  is  correct,  quinone  may  be  regarded 
as  derived  from  a  dibasic  acid  in  the  same  way  that  a  simple 
ketone  is  derived  from  a  monobasic  acid.  Thus,  the  calcium 


salt  of  an  acid  of  the  formula  C2H2< 


COOH 


ought,  according 


to  this  view,  to  yield  quinone  by  distillation:  — 


< 


co~o 


r 

>Ca 


CO 

CO 


Several  quinones  have  been  studied.  Under  the  head  of 
Anthracene  we  shall  meet  with  an  important  one  called  anthra- 
quinone,  which  has  been  made  by  reactions  that  prove  it  to  be 
a  di-ketone  in  the  sense  in  which  this  expression  is  explained 
above. 


Ortho-benzoquinone,  isomeric  with  the  well-known  para 
compound,  has  recently  been  prepared  from  pyrocatechol. 
It  is  probably  to  be  represented  by  the  formula  :  — 


350  DERIVATIVES    OF    THE    BENZENE    SEEIES 

PYRIDINE  BASES,  CnH2n_5K 

The  pyridine  bases  are  formed  in  the  distillation  of  bones, 
certain  bituminous  shales,  and  coal,  and  were  first  isolated  from 
bone  oil,  which  is  a  complex  mixture  of  many  substances.  At 
present  these  bases  are  obtained  principally  from  coal  tar.  The 
principal  members  of  the  group  are  pyridine,  picoline,  lutidine, 
and  collidine.  They  form  an  homologous  series :  — 

Pyridine C5H5N 

Picoline C6H7N 

Lutidine C7H9N 

Collidine C8HnN 

The  formation  of  these  bases  in  the  distillation  of  bones  is 
due  to  the  presence  of  acrolei'n,  ammonia,  methylamine,  etc., 
and  their  action  upon  one  another  at  high  temperatures. 
Members  of  the  series  are  formed  whenever  aldehydes  of  the 
fatty  series  are  heated  with  ammonia.  For  example,  ordinary 
aldehyde  and  ammonia  give  methyl-ethyl-pyridine,  C8HUN, 
[C6H3(CH3)(C2H5)N]:- 

4  C2H40  +  NH3  =  C8HUN  +  4  H20  j 
and  acrolei'n  and  ammonia  give  /3-picoline :  — 

2  C3H40  +  NH3  =  C6H7N  +  2  H20. 

Pyridine  and  picoline  are  also  formed  when  glycerol  is 
distilled  with  ammonium  sulphate  and  sulphuric  acid. 

An  interesting  synthesis  of  pyridine  is  effected  by  passing 
acetylene  and  hydrocyanic  acid  together  through  a  heated 
tube.  This  is  analogous  to  the  synthesis  of  benzene  from 
acetylene:-  3C2H2  =  C6H6; 

2  C2H2  +  HCIST  =  C5H5N. 

Pyridine  can  also  be  made  from  penta-methylene-diamine  by 
first  subjecting  the  hydrochloric  acid  salt  of  this  substance  to 
dry  distillation  and  heating  the  product  thus  formed  with  sul- 
phuric acid :  — 


PYRIDINE  351 

nw      CH2 .  CH2 .  NH3C1.       p         CH2.CH2  CH  =  CH     „ 

'H2<CH2 .  CH2 .  NH2  !<CH2 .  CH2>  IC^CH-CH^N 

Pyridine,  C5H5N. — Pyridine  is  found  in  commercial  am- 
monia, and  is  formed,  as  stated  above,  in  the  distillation  of 
bones,  of  certain  bituminous  shales,  and  of  coal.  It  has  been 
prepared  from  a  number  of  its  carboxyl  derivatives,  as,  for 
example,  from  nicotinic  acid,  C5H4N .  GO2H,  which  is  formed 
when  nicotine  is  oxidized  with  nitric  acid.  The  formation  of 
pyridine  from  quinolinic  acid,  a  dicarboxyl  derivative  of  pyri- 
dine,  is  of  special  importance,  as  it  leads  very  clearly  to  a  con- 
ception of  the  constitution  of  pyridine.  Quinoline  (which  see) 
will  be  shown  to  have  the  constitution  represented  by  the 
formula  — 

HC     CH 


H 


When  it  is  oxidized  it  gives  the  dibasic  acid  above  referred  to, 
quinolinic  acid, 


When  this  is  distilled  with  lime  it  loses  carbon  dioxide  and 
gives  pyridine :  — 

CH 

xv     /"I    XV_W2JLJL  xv 

nor  v  HC/^CH 

+  2  C02. 


352  DERIVATIVES    OF   THE   BENZENE   SERIES 

According  to  this,  pyridine  is  benzene  containing  a  nitrogen 
atom  in  place  of  one  of  the  CH  groups.  The  question  in  re- 
gard to  the  linkage  of  the  groups  and  atoms  in  pyridine  is  a 
difficult  one  to  deal  with,  and  it  need  not  be  discussed  here. 
Suffice  it  to  say  that  the  above  hypothesis,  as  to  the  relation 
between  benzene  and  pyridine,  is  in  accordance  with  all  the 
facts  known. 

Pyridine  is  a  liquid  with  a  peculiar,  sharp,  characteristic 
odor.  It  is  miscible  with  water  in  all  proportions.  It  boils 
at  115°.  It  acts  like  a  monacid  base,  forming  salts  like 
C5H6N  .  HC1,  C5H5N  .  HN03,  C5H5N  .  H2S04,  etc.  It  unites  with 
alkyl  iodides  like  methyl  iodide,  ethyl  iodide,  etc.  When 
these  compounds  are  treated  with  silver  hydroxide,  they  form 
the  corresponding  hydroxides,  which  are  strong  bases.  The 
compounds  with  the  alkyl  iodides  are  converted  by  heat  into 
salts  of  homologues  of  pyridine.  For  example,  the  ethyl  iodide 
addition-product  of  pyridine  is  transformed  at  290°  into  ethyl- 
pyridine  hydriodide  :  — 

C5H5N  .  C2H5I  =  C2H5  .  C5H4N  .  HI. 

The  view  above  presented  has  suggested  various  lines  of  in- 
vestigation. Thus,  if  the  above  formula  represents  the  rela- 
tions between  benzene  and  pyridine,  it  is  clear  that  the  existence 
of  three  isomeric  mono-substitution  products  of  pyridine  ought 
to  be  possible.  For  example,  there  should  be  three  methyl- 
pyridines  or  picolines,  three  pyridine-carbonic  acids,  etc.  The 
three  picolines  should  correspond  to  the  formulas 


H  H 

HC/  \CH      HC/  \C.CH    HC/  \ 


I 

HCL 
\ 


CH 

I  II  II 

C.CH3        HCV         CH  HCv         CH 


Ortho-picoline  Meta-picoline  Para-picoline 

All  three  picolines  are  known  ;  and,  by  oxidation,  they  are 


CONINE  353 

converted  into  the  three  pyridine-carbonic  acids,  C5H4N  .  C02H  ; 
and  these,  when  distilled  with  lime,  yield  pyridine  and  carbon 
dioxide. 

Lutidines,  C5H3(CH3)2N.  —  No  less  than  six  isomeric  vari- 
eties of  dimethylpyridine  are  possible  according  to  the  theory. 
Five  of  these  have  been  prepared  in  pure  condition.  By  oxida- 
tion they  yield,  first,  monobasic  acids,  and  then  dibasic  acids. 
When  the  monobasic  acids  are  distilled  with  lime,  they  yield 
picolines.  The  dibasic  acids  give  pyridine  :  — 


C02H  5 

PO  TT 
NC5H3<^^  =  NC5H5  +  2  C02. 

Conyrine,  propylpyridine,  NC5H4.C3H7.  —  This  base  is 
formed  when  conine  is  heated  with  zinc  chloride  or  when  the 
hydrochloride  of  conine  is  heated  with  zinc  dust.  It  is  con- 
verted into  picolinic  acid  by  oxidation,  and  is  reduced  to  conine 
by  hydriodic  acid. 

The  pyridine  bases  unite  with  two,  four,  or  six  atoms  of 
hydrogen.  Some  of  the  alkaloids  are  derivatives  of  the  addi- 
tion-products thus  formed. 

Piperidine,  C5HnN.  —  This  base  is  formed  from  piperine,  a 
constituent  of  pepper.  It  has  been  made  by  adding  hydrogen 
to  pyridine  by  means  of  sodium  and  alcohol  :  — 


/CH2-CH-C3H7 
Conine,  propylpiperidine,  CH2  \NH        .—This 


base  occurs  together  with  others  in  hemlock  (Coniummaculatum). 


354 


DERIVATIVES    OF   THE   BENZENE   SERIES 


It  is  a  colorless  liquid,  and  is  a  violent  poison.  This  is  the 
first  alkaloid  that  was  prepared  artificially,  and  it  is  therefore 
of  special  interest.  The  steps  taken  are  indicated  below  :  — 


CH2OH 

CH 

II 
CH2 


Allyl 
alcohol 


CH2Br 
I 
>-  CH      - 

II 
CH2 

Allyl  bromide 


CH2Br 
I 
CH2    - 

I  I 

CH2Br          CH2CN 


I 
CH2 


Tri-methylene 
bromide 


Tri-methlene 


cyanide 


£ 


CH2 

1 
CH2 

1 
CH2 


N 


CONH2        CH2CH2NH2 

I 
CH2  — 

I 
CONH2  CH2CH2NH2 

Penta-methvlene  diainine 


HC/\C. 


CH 


CH 


HC/\C.CH  =  CH.CH3         H2C/\CH.CH2.CH2.  CH3 


CH 


CH2 

Inactive  conine 


The  change  from  picoline  to  allyl-pyridine  is  effected  by 
means  of  paraldehyde.  The  conine  thus  obtained  is  optically 
inactive,  whereas  that  obtained  from  hemlock  is  dextro-rotatory. 
By  means  of  the  salt  with  d-tartaric  acid,  the  inactive  conine 
can  be  resolved  into  the  two  active  varieties.  The  d-conine 
thus  obtainec^  is  identical  with  natural  conine. 

[Is  there  an  asymmetric  carbon  atom  in  conine  ?] 


HEMITERPENES  355 

TERPENES  AND  CAMPHORS 

Terpenes  are  hydrocarbons  found  in  various  coniferous  trees 
and  in  plants  of  the  citrus  varieties.  The  so-called  ethereal 
oils  are  obtained  from  such  plants  and  their  fruits  by  distilla- 
tion with  water  vapor.  Some  of  these  ethereal  oils  are  mixtures 
of  hydrocarbons  of  the  formula  C10H16  with  other  compounds 
containing  oxygen.  The  principal  terpenes  have  the  for- 

•  P  FT 

mula  C10H16  and  are  related  to  hexahydrocyinene,  C6H10<C  ^  . 

Others  are  related  to  tetrahydrocymene,  and  still  others  to 
dihydrocymene.  Some  take  up  one  molecule  of  hydrochloric 
acid  or  two  atoms  of  bromine,  others  take  up  two  molecules  of 
hydrochloric  acid  or  four  atoms  of  bromine.  They  also  com- 
bine with  water  to  form  hydrates.  They  are  easily  polymer- 
ized by  heat  or  by  shaking  with  sulphuric  acid  or  boron 
fluoride.  Many  are  converted  into  cymene  by  gentle  oxi- 
dation, and  by  more  energetic  oxidation  into  p-toluic  and 
terephthalic  acids. 

The  broadest  classification  of  the  terpenes  is  into  (1)  Hemi- 
terpenes,  C5H8;  (2)  Terpenes,  C10H16;  (3)  Sesquiterpenes,  C1SH24; 
(4)  Diterpenes,  C^H^ ;  (5)  Poly  terpenes,  (C^H^),,.. 

(1)  HEMITERPENES 

Isoprene,  C5H8.  —  This  is  formed  in  the  distillation  of  caout- 
chouc or  india  rubber.  It  has  been  shown  to  be  fi-methyl-divinyl, 
H2C  =  C(CH8)  -  CH  =  CH2.  When  heated  to  100°  in  a  sealed  tube 
with  glacial  acetic  acid  it  gives  a  product  identical  with  natural 
india  rubber.  This  is  the  basis  of  the  efforts  to  produce  india 
rubber  artificially  on  the  large  scale. 


(2)  TERPENES 
These  are  classified  into  Monocydic  and  Bicyclic  Terpenes. 


356  DERIVATIVES    OF   THE   BENZENE   SERIES 


A.   Monocydic  Terpenes 

The  characteristic  property  of  these  is  the  power  to  take 
up  four  atoms  of  bromine  or  two  molecules  of  the  halogen 
acids.  The  principal  ones  are  limonene  and  dipentene,  the 
latter  being  the  inactive  variety  of  the  two  optically  active 
limonenes. 

Limonene,  C10H16.  —  The  dextro  variety  is  found  in  oil  of 
lemon,  oil  of  bergamot,  and  a  number  of  other  ethereal  oils. 
Oil  of  orange  is  almost  entirely  d-limonene.  With  bromine  it 
forms  a  tetra-bromide,  C10H16Br4,  m.  p.  104°-105°.  Z-Limonene 
is  found  in  the  oil  of  fir  needles  (Pinus  sylvestris)  and  in  oil  of 
fir,  together  with  /-pinene.  Inactive  limonene  or  dipentene 
occurs  with  cineol  in  Oleum  cince,  and  is  formed  by  heating 
pinene  and  camphene  to  250°-300°,  and  is  therefore  contained 
in  Russian  and  Swedish  oil  of  turpentine. 


B.   Bicyclic  Terpenes 

These  combine  with  one  molecule  of  hydrobrornic  acid  and 
with  two  atoms  of  chlorine  or  of  bromine  and  with  one  mole- 
cule of  water.  The  two  most  important  members  of  this  group 
are  pinene  and  camphene. 

Pinene,  O10H16. — This  is  the  principal  ingredient  of  the  vari- 
ous kinds  of  oil  of  turpentine  obtained  from  different  varieties  of 
pine.  Heated  to  250°-270°  it  is  converted  into  dipentene  or 
inactive  limonene.  It  is  known  in  three  varieties  —  dextro, 
levo,  and  inactive.  d-Pinene  is  obtained  from  American,  Ger- 
man, and  Swedish  oil  of  turpentine ;  /-pinene  from  the  French. 
The  inactive  variety  is  formed  by  combination  of  the  two  active 
varieties.  The  evidence  points  to  the  following  formula  as  the 
most  probable  for  pinene :  — 


BICYCLIC   TERPENES  357 

CH2  -  CH    -    CHa 
CH3-C-CH3 


JH  =   C     -     CH 
CH3 

This  significance  of  the  adjective  "bicyclic"  will  be  apparent. 

d-Pinene  hydrochloride,  bornyl   chloride,   Ci0Hi7Cl,  is 

formed  by  conducting  dry  hydrochloric  acid  gas  into  pinene. 
It  is  a  crystalline  solid  with  an  odor  like  that  of  ordinary  cam- 
phor. When  heated  alone,  or  with  bases,  hydrochloric  acid  is 
split  off  and  camphene  which  is  isomeric  with  pinene  is  formed. 

Oil  of  Turpentine.  —  When  incisions  are  made  in  the  trunk 
of  various  conifers,  a  liquid  exudes  that  is  known  as  turpen- 
tine. Most  of  that  which  comes  into  the  market  is  obtained 
from  Pinus  austmUs,  growing  in  North  America.  The  volatile 
constituent  of  turpentine  is  oil  of  turpentine.  The  non-volatile 
constituent  is  abietic  acid,  C^HgoOg.  These  are  separated  by 
distillation.  If  the  distillation  is  carried  on  without  the  addi- 
tion of  water,  the  residue  is  ordinary  rosin  (colophony). 

Oil  of  turpentine  dissolves  sulphur,  phosphorus,  and  caout- 
chouc, and  is  used  in  the  preparation  of  varnishes  and  oil 
colors. 

Camphene,  C10H16. — This  is  formed  from  bornyl  chloride 
(which  see)  and  also  from  borneol.  From  d-bornyl  chloride 
d-camphene  is  obtained ;  and  from  /-bornyl  chloride  Z-camphene. 
Camphene  probably  has  the  formula 

r\-rr  PIT          PTI 

l^-ilo  —  v^-TL  —  v^-tl2 

CH3 .  C  .  CH3 
H2 J CH 

Cu| 

CH2 


358  DERIVATIVES    OF    THE   BENZENE   SERIES 

Comparing  this  with  the  formula  of  pinene  it  is  evident  that 
the  passage  from  pinene  through  bornyl  chloride  to  camphene 
is  by  no  means  simple. 

Camphane,  CioHi8)  is  formed  from  bornyl  iodide  by  reduc- 
tion, and  is  the  saturated  hydrocarbon  corresponding  to  cam- 
phor and  borneol.  (See  p.  360.) 

(3)    SESQUI-  AND  POLYTERPENES 


Caoutchouc,  (CioHie)*-  —  This  is  commonly  known  as  india 
rubber.  It  is  the  hardened  milky  juice  of  the  tropical  euphor- 
biacese,  apocynese,  etc.,  especially  of  Siphonia  (Jicus)  elastica 
of  Brazil.  By  dissolving  the  crude  material  in  chloroform 
and  precipitating  with  alcohol  it  can  be  obtained  pure,  in  the 
form  of  a  white,  amorphous  mass.  By  treatment  with  sul- 
phur it  is  vulcanized,  the  product  being  much  harder  than  the 
caoutchouc  itself.  Treated  with  ozone  and  water  it  is  split  into 
two  molecules  of  levulinic  aldehyde,  CH3  .  CO  .  CH2  .  CH2  .  CHO. 
Now  it  has  been  shown  that  the  effect  of  treatment  with  ozone 
and  water  is  to  add  three  atoms  of  oxygen  to  each  pair  of  car- 
bon atoms  united  by  double  bonds  and  to  cause  a  breaking 
down  at  these  parts  of  the  molecule.  In  this  case  the  action 
is  indicated  thus  :  — 

/(CH2)2  .  CH^ 

CH3  .  C/  >C  .  CH3+2  03+2  H20=2  CH3  .  CO  .  (CH2)2  .  CHO 

\CH.(CH2)2/ 


Further,  it  has  been  pointed  out  that  isoprene  (which  see)  is 
easily  polymerized  to  caoutchouc.  These  formulas  will  be 
helpful  in  this  connection :  — 

CH2=CH\  /CH2.CH2. 


y?CH2  CH2=CH\  /CM2 .  (JM2 .  UM^V 

H3C .  Cf  >C  .  CH3  -->  CH3 .  C^  >C . CII3. 

\CH=CH2  H2C^  ^CH .  CH2 .  CH2/ 

2  Mol.  Isoprene  This  polymerizes  to  form  (CioHi6)a;. 


SESQUI-    AND    POLYTERPENES  359 

CAMPHORS 

Ordinary  camphor  is  the  best  known  example  of  these. 
They  are  either  ketones  or  alcohols.  By  reduction  with  alco- 
hol and  sodium  the  ketone  camphors  are  converted  into  alcohol 
camphors,  and  the  alcohol  camphors  are  converted  into  ketone 
camphors  by  oxidation.  The  hydroxyl  group  of  the  alcohol 
camphors  can  be  replaced  by  halogen,  and  the  compounds  thus 
obtained,  when  treated  with  alcoholic  alkali,  give  up  the  halo- 
gen and  hydrogen  and  yield  terpenes.  Thus  borneol,  C10H17 .  OH, 
gives  bornyl  chloride,  C10H17C1,  and  this  in  turn  gives  camphene 
(which  see). 

A.   Monocydic  Camphors 

These  are  derived  from  the  monocyclic  terpenes.  The  prin- 
cipal one  is 

^-Menthol,  C10H19OH,  a  solid,  melting  at  42°  and  boiling  at 
212°,  which  is  the  principal  ingredient  of  the  oil  of  pepper- 
mint. It  has  been  shown  to  be  a  hydroxyl  derivative  of 
hexahydrocymene,  C^H^. 

B.   Bicydic  Camphors 

The  principal  members  of  this  group  are  related  to  camphene 
and  camphane.  They  are  borneol  and  laurinol 

Borneol,  Borneo  camphor,  C10H18O[C10H17(OH)]. — Borneo 
camphor  occurs  in  cavities  in  a  tree  (Dryobalanops  camphora) 
found  in  Borneo,  Sumatra,  etc.  This  variety  is  dextro-rota- 
tory. The  levo-rotatory  variety  is  found  in  the  camphor 
from  valerian  oil,  and  inactive  borneol  is  formed  by  bringing 
together  d-  and  /-borneol.  Borneol  is  much  like  ordinary  cam- 
phor, but  its  odor  resembles  that  of  pepper.  Treated  with 
sodium  and  alcohol,  camphor  gives  d-  and  Z-borneol.  Both  the 


360  DERIVATIVES   OF   THE   BENZENE   SERIES 

active  varieties  give  camphor  by  oxidation ;  treated  with  phos- 
phorus pentachloride  borneol  gives  bornyl  chloride,  C10H17C1, 
identical  with  pinene  hydrochloride. 

Camphor,  CioHi6O-  —  This  is  the  substance  ordinarily  called 
camphor.  It  is  obtained  in  China  and  Japan  from  different 
species  of  the  genus  Camphora  of  the  Laurus  family  by  dis- 
tilling the  finely  cut  wood  with  water  vapor.  It  is  purified  by 
sublimation.  It  is  a  colorless  mass  that  can  be  crystallized  from 
alcohol  and  sublimes  in  lustrous  prisms.  The  ordinary  form  is 
dextro-rotatory.  Both  the  other  possible  stereo-isomeric  forms 
are  known.  Camphor  is  reduced  to  borneol  by  hydrogen  from 
sodium  and  alcohol.  It  can  be  made  by  oxidizing  borneol  or 
camphene.  When  distilled  with  phosphorus  pentoxide,  cam- 
phor gives  cymene.  The  same  decomposition  is  effected  by 
heating  it  with  concentrated  hydrochloric  acid  to  170°. 

The  reactions  of  camphor  show  that  it  is  a  saturated  ketone. 
The  ease  with  which  it  is  converted  into  cymene  makes  it 
highly  probable  that  a  methyl  group  and  an  isopropyl  group  are 
present  in  the  compound  in  the  para  position  in  a  benzene  ring. 
When  heated  with  iodine  it  gives  carvacrol  by  loss  of  two 
atoms  of  hydrogen.  Carvacrol  is  isomeric  with  thymol,  the 
hydroxyl  being  in  the  ortho  position  to  the  methyl  group. 
This  makes  it  appear  highly  probable  that  the  oxygen  in  cam- 
phor is  ortho  to  methyl.  Other  facts  that  have  been  brought 
to  light  in  investigations  of  the  oxidation-products  of  camphor 
indicate  that  the  group,  C(CH3)2,  formed  from  isopropyl,  is 
united  with  two  para  carbon  atoms  of  the  benzene  ring.  All 
this  is  shown  by  the  formula  for  camphor  given  below,  now 
generally  accepted  by  chemists. 
CH2  —  CH  —  CH2  H2C  —  CH  —  CH2  H2C  —  CH  —  CH2 

H3C.C.CH3  H3C.C.CH3  H3C  .  C .  CH3 


H2C  —  C    —    CH2    H2C    —    C    —    CH(OH)   H2C    —    C    —    CO 

CH8  CH3  CH3 

Camphane  Borneol  Camphor 


BICYCLIC  CAMPHORS  361 

Artificial  Camphor.  —  Camphor  is  now  manufactured  from 
pinene.  The  steps  involved  are  (1)  addition  of  hydrochloric 
acid  and  formation  of  bornyl  chloride;  (2)  treatment  of  the 
bornyl  chloride  with  bases  and  formation  of  camphene ;  (3)  heat- 
ing of  camphene  with  acetic  and  sulphuric  acids  with  formation 
of  isobornyl  acetate ;  (4)  hydrolysis  of  isobornyl  acetate,  and 
oxidation  of  the  resulting  isoborneol  to  camphor. 


Although  not  closely  related  to  the  terpenes,  two  substances 
of  similar  composition  may  be  mentioned  in  this  connection. 
These  are  the  hydrocarbon  anhydrogeraniol  and  the  oxygen 
compound  geraniol. 

Anhydrogeraniol,  Ci0Hi6,  is  formed  from  geraniol,  C10H180, 
by  elimination  of  water.  It  probably  has  the  structure  repre- 
sented by  the  formula,  — 

(CH3)2C  =  CH .  CH2 .  CH2 .  C(CH3)  =  C  =  CH2. 

Geraniol,  Ci0Hi8O,  is  contained  in  Indian  oil  of  geranium 
and  a  number  of  other  ethereal  oils.  It  is  a  primary  alcohol, 
giving  an  aldehyde  geranial,  C10H160,  and  an  acid,  geranic  acid, 
C10H1602,  by  oxidation.  Geranial  loses  water  and  gives  cymene. 


CHAPTER   XVI 


DI-PHENYL-METHANE,  TRI-PHENYL-METHANE,   TETRA- 
PHENYL-METHANE,  AND  THEIR  DERIVATIVES 

As  we  have  seen,  toluene  may  be  regarded  either  as  methyl- 
benzene  or  phenyl-methane.  Of  course,  according  to  all  that 
is  known  regarding  similar  substances,  the  two  views  are  identi- 
cal. Regarding  it,  for  our  present  purpose,  as  phenyl-methane, 

C6H5 
H 
H 
H 

This  suggests  the  possibility  of  the  existence  of  such  sub- 
stances as 

06H5 


we  may  write  its  formula  thus  :   c 


Di-phenyl-methane 


Tri-phenyl-methane C 


and  Tetra-phenyl-methane 


All  these  hydrocarbons  are  known.     The  derivatives  of  tri- 
phenyl-methane  are  of  special  interest  and  importance. 

There  is  one  reaction  by  means  of  which  these  hydrocarbons 

362 


TRI-PHENYL-METHANE  363 

can  be  made  very  readily.  It  has  also  been  used  for  the  synthe- 
sis of  many  other  hydrocarbons.  It  depends  upon  the  remark- 
able fact  that,  when  a  hydrocarbon  is  brought  together  with  a 
compound  containing  chlorine,  and  anhydrous  aluminium  chlo- 
ride then  added,  hydrochloric  acid  is  evolved,  and  union  of  the 
two  substances  is  effected,  the  aluminium  chloride  not  entering 
into  the  composition  of  the  product  (Friedel-Crafts  reaction). 
Thus,  when  benzene  and  benzyl  chloride,  C6H5  .  CH2C1,  are 
brought  together  under  ordinary  circumstances,  no  action  takes 
place  ;  but,  if  some  solid  aluminium  chloride  is  added,  reaction 
takes  place  according  to  the  following  equation  :  — 

C6H5.CH2C1  -f-  C6H6  =  CgHg.CH^.CgHs  +  HCl, 

Di-phenyl-methane 

and  di-phenyl-methane  is  formed. 

Similarly,  when  chloroform  and  benzene  are  brought  together 
in  the  presence  of  aluminium  chloride,  tri-phenyl-methane  is 
formed  according  to  this  equation  :  — 

CHC13  +  3  C6H6  =  CH  (C6H5)3  -f  3  HC1. 

Tri-phenyl-methane 

Another  method  by  which  these  hydrocarbons  can  be  made, 
consists  in  heating  a  chloride  and  a  hydrocarbon  together  in  the 
presence  of  zinc  dust.  Thus,  benzyl  chloride  and  benzene  give 
di-phenyl-methane  when  boiled  with  zinc  dust;  and  benzal 
chloride,  C6H5  .CHC12,  and  benzene  give  tri-phenyl-methane  :  — 

C6H5  .  CHC1,  +  2  C6H6  =  CH(C6H5)3  +  2  HC1. 
Only  tri-phenyl-methane  will  be  treated  of  here. 


Tri-phenyl-methane,  CigHieECHCCeH^s]-  —  This  hydrocar- 
bon can  be  made,  as  above  described,  from  benzal  chlo- 
ride and  benzene,  and  from  chloroform  and  benzene.  It 
can  also  be  made  from  benzal  chloride  and  mercury  diphenyl, 


364  DI-PHENYL-METHANE,   ETC. 

C6H5  .CHC12  +  Hg(C6H5)2  =  CH(C6H5)3  +  HgCl» 

It  forms  lustrous,  thin  laminse,  which  melt  at  92°.  It  is 
insoluble  in  water ;  easily  soluble  in  ether  and  chloroform.  It 
is  crystallized  best  from  alcohol. 

Towards  reagents  it  is  very  stable.  Thus,  ordinary  concen- 
trated sulphuric  acid  does  not  act  upon  it.  fC6H5 

I      /•>       TT 

Oxidizing  agents  convert  it  into  tri-phenyl-carbinol,  C  \  C6H5. 

lOH 

That  the  oxidation-product  is  really  tri-phenyl-carbinol  appears 
probable,  from  the  fact  that  whenever  aromatic  hydrocarbons 
that  contain  paraffin  residues  are  oxidized,  the  paraffin  resi- 
dues are  first  attacked,  while,  as  a  rule,  the  benzene  residue  is 
unacted  upon.  Further,  it  gives  an  acetate  with  acetyl  chlo- 
ride; and  with  phosphorus  pentachloride  it  gives  a  chloride 
which  is  decomposed  by  boiling  water,  giving  the  carbinol 
again.  A  bromide  is  formed  by  treating  it  with  hydrobromic 
acid,  and  this  gives  the  carbinol  when  boiled  with  water. 


s 

formed  by  treating  triphenyl-ra  ethane  with  nitric  acid;  and 
also  by  treating  a  mixture  of  nitro-benzene  and  chloroform 
with  aluminium  chloride:  — 


CHC13  +  3  C6HS.  N02  =  CH(C6H4.  N02)3  -h  3  HC1. 

This  reaction  shows  that  in  the  tri-nitro  product  one  nitro 
group  is  contained  in  each  benzene  residue. 


Triamino-triphenyl-methane,  para-leucaniline, 

C19H13(NH2)3[CH(C6H4.  NH2)3]— 

The  tri-amino  compound  is  made  by  reduction  of  the  tri-nitro 
compound,  and  also  by  reduction  of  para-rosaniline.  It  is 
converted  into  para-rosaniline  by  oxidation. 


PARA-ROSANILINE  365 

TRI-PHENYL-METHANE  DYES 

The  well-known  substances  included  under  the  head  of  Tri- 
phenyl-methane  Dyes  are  more  or  less  simple  derivatives  of 
the  two  compounds  called  rosaniline  and  para-rosaniline. 

When  mixtures  of  aniline  with  ortho-  and  para-toluidines 
are  heated  with  oxidizing  agents,  such  as  arsenic  acid,  stannic 
chloride,  mercuric  chloride,  etc.,  several  substances  are  formed, 
the  principal  of  which  are  the  two  above  named.  Para-rosan- 
iline, Ci9H19N"30,  is  formed  from  para-toluidiue  and  aniline, 
according  to  the  equation,  — 

2  C6H7N  +  CyH^  +  30  =  C19H19N30  +  2  H2O. 

Aniline          p-Toluidine  Para-rosaniline 

Kosaniline,  C2oH21N30,  is  formed  in  a  similar  way :  — 
C6H7N  +  2  C7H9N  +  30  =  C20H21N30  +  2  H20. 

Aniline     o-  and  p-Toluidine  Eosaniline 

The  composition  and  modes  of  formation  of  the  two  sub- 
stances show  that  rosaniline  is  a  homologue  of  para-rosaniline, 
the  relation  between  the  two  substances  being  represented  by 
the  formulas  C19H19N30  and  C19H18(CH3)]Sr30. 

By  treating  para-rosaniline  with  a  reducing  agent,  it  is  con- 
verted into  para-leucaniline,  which  has  been  shown  to  be  tri« 
amino-triphenyl-methane :  — 


C19H19N-30+H2 

Para-rosaniline 


fC6H4.NH2] 
CH    C6H4.NH2 


+  H20. 


It  will  thus  be  seen  that  para-rosaniline  and  rosaniline,  which 
are  the  fundamental  compounds  of  the  group  of  aniline  dyes, 
are  derivatives  of  the  hydrocarbon  tri-phenyl-methane. 

Para-rosaniline,  C19H19N3O.  —  The  formation  of  this  sub- 
stance by  oxidation  of  para-leucaniline  and  of  a  mixture  of 
toluidine  and  aniline  was  mentioned  above.  The  relation 


366  DI-PHENYL-METHANE,    ETC. 

between  para-rosaniline  and  para-leucaniline  is  expressed  by 
the  following  formulas :  — 

C6H4.NH2  [C6H4.NH2 

C6H4 .  NH,    C  (OH)    C6H4 .  NH2 . 
C6H4.NH2  IC6H4.NH2 

Triamino-triphenyl-methane,    Triamino-triphenyl-carbinol, 
or  Para-leucaniline  or  Para-rosaniline 

Bosaniline,  C2oH2iN3O.  —  This  is  the  principal  constituent 
of  commercial  f uchsine.  It  is  formed  by  oxidizing  a  mixture  of 
aniline  with  ortho-  and  para-toluidines  :  — 

C6H7N  +  2  C7H9N  +  30  =  C^H^O  +  2  H20. 

Experiment  76.  In  a  dry  test-tube  put  a  little  dry  mercuric  chlo- 
ride and  a  few  drops  of  commercial  aniline.  Heat  over  a  small  flame. 
Dissolve  the  product  in  alcohol,  with  the  addition  of  a  little  hydrochloric 
or  acetic  acid.  The  beautiful  color  of  the  solution  is  due  to  the  presence 
of  the  hydrochloride  or  acetate  of  rosaniline. 

On  the  large  scale,  the  oxidizing  agent  used  is  arsenic  acid. 
Care  is  taken  to  remove  all  arsenic  acid  from  the  product,  but 
it  is  nevertheless  sometimes  found  in  the  products  obtained  in 
the  market.  Nitro-benzene  is  also  used  as  the  oxidizing  agent. 
In  this  case  there  is,  of  course,  no  arsenic  in  the  product. 
Rosaniline  crystallizes  in  needles  or  plates.  It  is  very  slightly 
soluble  in  water;  more  readily  soluble  in  alcohol.  It  forms 
three  series  of  salts  with  monobasic  acids.  With  hydrochloric 
acid  it  forms  the  salts  C^H^ .  HC1  and  C^H^Ng .  3  HC1. 
Fuchsine  or  magenta  is  a  mixture  of  the  hydrochlorides  of 
rosaniline  and  para-rosaniline.  The  formation  of  the  salts  of 
para-rosaniline  takes  place  as  represented  in  the  following 
equation :  — 

fC6H4.NH2 
C  (OH)(C6H4 .  NH2)3  +  HC1  =  C    C6H4 .  NH2  +  H20 


Para-rosaniline 


C6H4.KH.HC1 

I 


Para-rosaniline  hydrochloride 


ROSANILINE 


367 


Instead  of  the  formula  here  given  for  the  salt  two  others 
have  been  suggested.  In  one  of  these  the  salt  is  represented 
as  derived  from  the  base  triamino-triphenyl-carbinol  or  para- 
rosaniline,  as  potassium  chloride  is  formed  from  potassium 
hydroxide :  — 

.C6H4]  NH2.C6H4] 

.  C«H4    C  (OH)  NH2 .  C6H4    CC1. 

NH,.C6HJ  NH2.C6H4J 

According  to  the  other  view  the  salt  and  all  the  colored  salts 
derived  from  para-rosaniline  and  similar  bases  have  a  constitu- 
tion similar  to  that  of  quinone,  as  shown  thus  for  the  hydro- 
chloric acid  salt  of  para-rosaniline  :  — 

H2N.H4C6V      /C6H4.NH2 
XX 


H 

or  (C6H4NH2)2C  :  C6H4 : 


NH2C1 

Fuchsine  and  the  other  salts  of  rosanilme  dye  wool  and  silk 
directly.  For  dyeing  cotton  cloth,  however,  a  mordant  is  gen- 
erally necessary. 

Dyeing.  Animal  fibres,  in  general,  are  colored  directly  by 
dyes ;  that  is  to  say,  they  have  the  power  of  forming  with  the 
dyes  stable  compounds  which  adhere  to  the  fibres.  This  is  not 
generally  true  of  vegetable  fibres,  as  cotton  cloth  and  linen. 
Hence,  in  order  to  dye  the  latter,  something  must  be  added 
that,  with  the  dye,  forms  a  compound  which  adheres  to  the 
fibres.  Substances  which  act  in  this  way  are  called  mordants. 
Among  the  substances  used  as  mordants  are  aluminium  acetate, 
ferric  acetate,  and  some  salts  of  tin. 


368  DI-PHENYL-METHANE,    ETC. 

Experiment  77.  Make  a  dilute  solution  of  picric  acid  by  dissolving 
2f  to  3&  in  200CC  to  300CC  water.  In  a  portion  of  it  suspend  a  few  pieces  of 
•white  yarn  or  flannel.  The  woollen  material  will  be  strongly  dyed  yellow. 
In  another  portion  suspend  a  piece  of  ordinary  cotton  cloth. 

It  should  be  noted  that  some  dyes  are  applicable  to  cotton 
without  mordants.  These  are  called  substantive  dyes. 

Acid  fuchsine  is  a  sulphonic  acid  of  rosaniline.  It  is 
formed  by  treating  rosaniline  with  concentrated  sulphuric  acid 
at  120°.  It  is  soluble  in  water,  and  is  a  valuable  dye. 

Aniline  dyes.  —  By  introducing  various  hydrocarbon  resi- 
dues into  para-rosaniline  or  rosaniline,  in  place  of  some  or  all 
of  the  hydrogen  atoms  of  the  amino  groups,  dyes  of  other 
colors  are  formed.  The  general  effect  of  introducing  methyl 
groups  is  to  form  dyes  of  a  violet  color.  As  the  number  of 
methyl  groups  increases,  the  product  has  a  deeper  blue  tint. 

Hexamethyl-para-rosaniline.  —  The  hydrochloric  acid 
salt  of  this  is  the  well-crystallized  dye,  crystal  violet, 
[C6H4.N(CH3)2]2C:C6H4:N(CH3)2C1.  It  is  one  of  the  prin- 
cipal constituents  of  methyl  violet.  Some  of  the  methods  used 
in  preparing  this  dye  are  of  special  interest.  It  is  made  — 

(1)  By  the  action  of  para-tetra-methyl-diamino-benzophenone 
on  dimethyl-aniline  in  the  presence  of  dehydrating  agents  — 


(2)  By  heating  dimethyl-aniline  with  carbonyl  chloride  and 
aluminium  chloride  or  zinc  chloride  :  — 


COCl2  +  2  C6H5.N(CHs)2=CO<432  +  2  HC1; 

t^6n4.l>i(^ii3;2 

CO  <    K'  +  C6H5.N(CH3)2HC1  = 


PHTHALEINS  369 

Methyl  violet  consists  of  crystal  violet  mixed  with  products 
containing  a  smaller  number  of  methyl  groups. 

Methyl  green  is  an  addition-product  formed  by  the  action  of 
methyl  chloride  on  an  alcoholic  solution  of  crystal  violet. 

Hofmann's  violet  (Dahlia)  is  either  the  hydrochloric  acid  or 
acetic  acid  salt  of  tri-methyl-rosaniline.  It  is-made  by  heating 
together  a  salt  of  rosaniline,  methyl  iodide,  and  methyl  alcohol. 

Aniline  blue  is  the  hydrochloride  of  tri-phenyl-rosaniline.  It 
is  formed  by  heating  salts  of  rosaniline  with  aniline  and  some 
benzoic  acid. 

/Soluble  blue  is  a  sulphonic  acid  of  aniline  blue. 

PHTHALEINS 

In  treating  of  phthalic  anhydride,  it  was  stated  that  when 
this  substance  is  treated  with  phenols,  phthalems  are  formed ; 
and,  in  treating  of  resorcinol,  a  markedly  fluorescent  body 
was  mentioned  as  being  formed  when  phthalic  anhydride  and 
resorcinol  are  heated  together. 

Phenol-phthalein,  C2oHuO4.  —  This  substance  is  formed  by 
heating  a  mixture  of  phenol  and  phthalic  anhydride  with  sul- 
phuric acid  or  some  other  dehydrating  agent :  — 

2  C6H60  +  C8H40,  =  C»H1404  +H20. 

Phenol  Phthalic  Phenol- 

anhydride          phthalein 

The  mass  is  boiled  with  water  to  remove  the  sulphuric  acid, 
dissolved  in  caustic  soda,  and  the  phenol-phthalein  precipitated 
by  the  addition  of  an  acid.  It  forms  a  granular  crystalline 
powder.  Its  solution  in  alkalies  is  red  or  violet,  according  to 
the  thickness  of  the  layer.  Acids  destroy  the  color.  Hence  it 
is  used  as  an  indicator  in  acidimetry  and  alkalimetry  as  a  sub- 
stitute for  litmus.  It  is  used  in  medicine  as  a  purgative. 

Phenol-phthalein,  like  rosaniline,  is  a  derivative  of  tri-phenyl- 
methane,  as  has  been  shown  by  the  following  somewhat  compli- 
cated reactions :  — 


370  DI-PHENYL-METHANE,   ETC. 

By  treating  phthalic  anhydride  with  phosphorus  pentachlo- 
ride,  phthalyl  chloride,  C8H402C12,  is  formed.  When  this  is 
treated  with  benzene  in  the  presence  of  aluminium  chloride,  the 
reaction  represented  in  the  following  equation  takes  place  :  — 

C8H402C12  +  2  C6H6  =  C8H402(C6H5)2  +  2  HC1. 

Phthalyl  chloride  Diphenyl-phthalide 

The  substance  thus  formed  is  known  as  diphenyl-phthalide. 
Its  conduct  towards  water  and  bases  is  such  as  to  show  that  it 
is  the  anhydride  of  an  acid  :  — 

C8H402(C6H5)2  +  KOH  =  C7H50  < 

652 

When  this  salt  is  reduced  by  means  of  zinc  dust  it  loses 
oxygen  :  — 


C;H5  +H20. 

(  C6H5)2 

And,  finally,  when  the  acid  is  distilled  with  baryta,  it  loses 
carbon  dioxide  and  yields  tri-phenyl-m  ethane  :  — 

(  PO  TT  (  ^6^5 

C7H5    £*!?    =  CH  J  C6H5  +  CO,. 
(C6H5)2  (CeH5 

We  have  thus  passed  from  phthalic  anhydride  to  triphenyl- 
methane,  and  the  reactions  just  referred  to  are  in  all  prob- 
ability correctly  represented  by  the  following  formulas  and 
equations  :  — 


c 


CH 


65 


C6H4.CO 
0 1 


+KOH=:=c 


C6H5 
C6H5 

C6H4.C02K. 
OH 


Diphenyl-phthalide,  or  an-  Potassium  triphenyl- 

hydride  of  triphenyl-car-  carbiuol-carbonate 

binol-carbonic  acid 


PHENOL-PHTH  A  LEIN 


371 


CH 


65 


C6H4.C02K  +  H2 
OH 


=  c- 


C6H5 
C6H5 

C6H4.C02H 
H 


C 


C6H5 

C6H5 

C6H4.C02K 

H 


Potassium  triphenyl- 
methane-carbonate 

C6H5 


+  H20. 


C6H5 
H 

Triphenyl-methane 

Now,  by  making  dinitro-diphenyl-phthalide,  reducing  it,  and 
boiling  the  diazo  compound  with  water,  the  product  obtained  is 
phenol-phthalei'n.  Hence,  the  latter  compound  appears  to  be 
the  dihydroxy  derivative  of  dipheiiyl-phthalide :  — 


C6H5 
C6H5 
C6H4.CO 

0  1 

C6H4.NH, 
C6H4.NH2 
C6H4.CO 

0  1 

] 

C6H4.OH 
C6H4.OH 
C6H4.CO* 
0  1 

Phenol-phthalein 

The   formula   for   phenol-phthalein    may    also   be    written 
thus  :  — 

C6H4.OH  C6H4 

C6H4.OH>     <0  '°' 

the  curious  arrangement  of  the  carbonyl  group  being  simply 
the  sign  of  the  anhydride  condition  between  carboxyl  and 
hydroxyl,  of  which  the  simplest  expression  is 

OTT 


This  plainly  is  the  characteristic  grouping  of  the  lactones 
(see  p.  169). 

There  is  reason  to  believe  that  when  a  phthalei'n  is  treated 
with  a  base  and  converted  into  a  salt  the  constitution  is  essen- 


372  FLUORESCEIN 

tially  changed,  the  resulting  salt  having  a  quinone-like  struc- 
ture, as  shown  thus :  — 


no 


CO 


Free  phenol-phthalem  M^flo-potassium  salt  of  phenol-phthalei'n 

(lactoid  formula)  (quinoid  formula) 

NOTE  FOR  STUDENT.  —  Although  the  reactions  above  briefly  described 
may  at  first  sight  appear  to  be  difficult  to  comprehend,  they  are  in  reality 
simple  enough.  The  student  is  earnestly  recommended  not  to  slight  them 
on  account  of  the  long  names  and  complex  formulas  involved.  They  afford 
an  excellent  example  of  the  methods  upon  which  we  rely  for  determining 
the  nature  of  complex  substances.  Notice  that  all  appears  dark  until  the 
well-known  substance  tri-phenyl-methane  is  obtained,  which  suggests  that 
all  the  substances  are  derivatives  of  this  fundamental  hydrocarbon  ;  and 
how  easily,  when  this  conception  has  once  been  formed,  the  interpretation 
of  all  the  reactions  follows. 

Among  the  other  phthaleins  that  deserve  special  mention  is 
that  which  is  formed  with  resorcinol. 


Fluorescei'n,  resorcinol-phthalei'n,  C2oH12O5  +  H2O.  — 
This  beautiful  substance  is  formed  by  heating  together  resor- 
cinol and  phthalic  anhydride  to  200°  :  — 

2  C6H4(OH)2  +  C8H403  =  C»HU05  +  2  H20. 

Its  solutions  in  alkalies  are  wonderfully  fluorescent.  The  sub- 
stance, which  is  sold  under  the  name  "uranin"  for  the  purpose 
of  exhibiting  the  phenomenon  of  fluorescence,  is  the  di-sodium 
salt  of  fluoresce'in. 

From  the  solutions  of  its  salts  fluoresce'in  is  precipitated  as  a 
yellow  powder  of  the  composition,  C2oH1406.  Heated  to  130° 
this  loses  water  and  forms  the  compound,  C^H^Os,  which  is 
yellowish  red.  The  fact  that  the  compound  is  colored  has  led 
to  the  belief  that  it  has  the  quinoid  structure  in  the  free  con- 
ditions as  well  as  in  its  salts. 


EOSIN  373 

The  reaction  that  takes  place  between  resorcinol  and  phthalic 
anhydride,  when  fluorescein  is  formed,  is  of  the  same  kind  as 
that  which  takes  place  between  phenol  and  the  anhydride. 
We.  should  therefore  expect  to  find  that  the  quinoid  form  of 
fluorescein  has  the  formula :  — 


COOH 


It  is  found,  however,  that  in  reality  fluorescein  corresponds  to 
the  above  formula  less  one  molecule  of  water;  and  it  is  believed 
that  the  structure  should  be  represented  thus :  — 


COOH 


Eosin,  C2oH6Br4O5K2,  is  formed  by  treating  fluorescein  with 
bromine,  and  then  with  potassium  carbonate.  Its  dilute  solu- 
tions have  an  exquisite,  delicate  pink  color  which  suggests  a 
color  characteristic  of  the  sky  at  the  dawn  of  day.  Hence  the 
name  of  eosin,  from  ^<os,  dawn.  It  is  fluorescent,  and  is  used 
as  a  dye.  It  is  a  di-potassium  salt  of  tetra-brom-fluorescein,  as 
shown  by  this  formula  :  — 

Br  Br 


COOK 


CHAPTER  XVII 
HYDROCARBONS,  CnH2n_8,  AND  DERIVATIVES 

THE  hydrocarbons  thus  far  treated  of  are  of  three  classes. 
They  are:  (1)  paraffins,  or  saturated  hydrocarbons  of  the 
marsh-gas  series  ;  (2)  un  saturated  hydrocarbons  related  to  the 
paraffins  ;  and  (3)  hydrocarbons  which  contain  residues  of  the 
saturated  paraffins  and  of  benzene. 

We  now  pass  to  a  brief  consideration  of  a  hydrocarbon  which 
is  made  up  of  a  residue  of  benzene  and  of  an  unsaturated  par- 
affin. It  bears  to  ethylene  the  same  relation  that  toluene  bears 
to  marsh  gas  ;  that  is  to  say,  it  is  phenyl-ethylene. 

Styrene,  phenyl-ethylene,  C8H8(C6H3  .  CH  :  CH2).  —  This 
hydrocarbon  is  contained  in  liquid  storax  —  a  fragrant,  honey- 
like  substance  which  exudes  from  various  plants,  as  the  liquid- 
ambar  —  and  in  coal-tar  xylenes.  It  is  formed  by  distilling 
cinnamic  acid  with  lime:  — 


NOTE  FOR  STUDENT.  —  What  does  this  reaction  suggest  with  regard  to 
the  relation  between  cinnamic  acid  and  styrene  ? 

It  is  also  formed  from  phenyl-ethane,  C6H5.C2H5,  in  the  same 
way  that  ethylene  is  formed  from  ethane  :  — 

(C2H6  +Br2     =C2H5Br  +  HBr 

(  C2H5Br  +  KOH  =  C2H4  +  KBr  +  H20  ' 


C6H5.C2H5      +Br2     =C6H5.C2H4 

CflH5.  C2H4Br  +  KOH  =  C6H5.  C2H3      +  KBr  +  H20. 


Styrene 
374 


CINNAMYL   ALCOHOL  375 

Its  formation  by  heating  acetylene  was  mentioned  on  page 
248:  — 


NOTE  FOR  STUDENT.  —  What  other  polymeric  product  is  obtained  by 
heating  acetylene  ? 

Styrene  is  a  liquid  of  an  aromatic  odor;  boils  at  140°; 
insoluble  in  water;  rniscible  with  ether  and  alcohol  in  all 
proportions. 

When  heated  alone  up  to  300°,  or  even  when  allowed  to  stand 
at  ordinary  temperatures,  it  is  converted  into  a  polymeric  modi- 
fication called  meta-styrene,  which  is  a  solid.  This  same  change 
is  readily  effected  by  several  reagents,  such  as  iodine  and  con- 
centrated sulphuric  acid.  Styrene  unites  directly  with  chlorine 
and  bromine  in  the  same  way  that  ethylene  does  (see  p.  232)  :  — 

C6H5.  CH:  CH2  +  2  Br  =  C6H5.  CHBr  .  CH2Br. 

It  unites  with  hydrobromic  acid,  forming  phenyl-ethyl 
bromide  :  — 

C6H5.CH:CH2  +  HBr  =  C6H5.CH2.CH2Br. 
Hydriodic  acid  reduces  it  to  phenyl-ethane  :  — 


Chromic  acid  and  other  oxidizing  agents  convert  styrene  into 
benzoic  acid  (see  remarks,  p.  269).  Some  higher  members  of 
this  series  have  been  prepared,  such  as  phenyl-propylene,  phenyl- 
butylene,  etc.  ;  but  at  present  they  are  not  of  sufficient  impor- 
tance to  make  their  consideration  necessary. 

Styrene  is  closely  related  to  cinnamic  acid,  which  in  turn  is 
related  to  the  interesting  and  important  compounds  of  the 
indigo  group. 


:  CH  .  CH2OH).- 

This  alcohol  occurs  in  nature  in  the  form  of  an  ethereal  salt  of 
cinnamic  acid  in  liquid  storax,  and  also  in  balsam  of  Peru. 


376         HYDROCARBONS,   (^H^g   AND   DERIVATIVES 

It  forms  long,  thin  needles,  which  melt  at  33°.  It  is  fairly 
soluble  in  water  ;  has  the  odor  of  hyacinths  ;  and  boils  at  250°. 
Nascent  hydrogen  converts  it  into  phenyl-propyl  alcohol, 
C6H5.CH2.CH2.CH2OH  (see  p.  317):  — 

C6H3.  CH:  CH.  CH2OH  +  H2  =  C6H5.  CH2.  CH2.  CH2OH. 

Hydriodic  acid  converts  it  into  propenyl-benzene  (phenyl- 
propylene),  C6H5.CH:CH.CH3,  and  toluene. 

When  oxidized  with  platinum  black  it  is  converted  into  the 
corresponding  aldehyde,  cinnamic  aldehyde,  the  chief  con- 
stituent of  the  oil  of  cinnamon;  and,  by  further  oxidation, 
into  cinnamic  acid.  The  relations  between  the  three  sub- 
stances are  the  familiar  ones  of  a  primary  alcohol,  and  the 
corresponding  aldehyde  and  acid  :  — 

C6H5.CH:CH.CH2OH.  C6H5.CH:CH.CHO. 

Styryl  alcohol  Cinnamic  aldehyde 

C6H5.CH:CH.C02H. 

Cinnamic  acid 

These  compounds  are  the  /?-phenyl  derivatives  of  allyl  alcohol, 
acrolein,  and  acrylic  acid  :  — 

CH2:CH.CH2OH.  CH2:CH.CHO.  CH2:CH.C02H. 

Allyl  alcohol  Acrolein  or  Acrylic  acid 

acrylic  aldehyde 


C8H802(C6H5  .  CH  :  CH  .  CO2H).  - 

Cinnamic  acid  is  found  in  liquid  storax,  partly  in  the  free  con- 
dition, and  partly  in  the  form  of  an  ethereal  salt  in  combina- 
tion with  styryl  alcohol,  as  styryl  cinnamate,  in  the  balsams  of 
Tolu  and  Peru.  It  can  be  made  synthetically  :  — 

1.   By  heating  together  benzoic  aldehyde  and  acetyl  chlo- 
ride :  — 

C6H5.  COH  -f  CH3.  COC1  =  C6H5.  C,H2.  C02H  +  HCL 


CIKNAMtC   ACID  377 

This  reaction  will  be  better  understood  by  writing  it  in  two 
equations :  — 

(1)  C6H5. CHJOJ  +  C;H2]H .  COC1  =  C6H5.  CH : CH .  COC1  +  H20 ; 

Cinnainyl  chloride 

(2)  C6H5.CH:CH.COC1  +  H20  =  C6H5.CH:CH.C02H  +  HC1. 

Cinnamyl  chloride 

The  kind  of  action  represented  in  equation  (1)  is  not  un- 
common. We  have  already  met  with  it  in  the  formation  of 
mesitylene  from  acetone  (see  p.  270),  in  which  case  two  hydro- 
gens from  each  of  three  methyl  groups  unite  with  an  oxygen 
atom  from  each  of  the  three  carbonyl  groups.  The  product  is 
called  a  condensation-product,  and  the  action  is  known  as  con- 
densation. It  has  already  been  referred  to  under  the  head  of 
aldol  condensation  (see  p.  191). 

2.  By  heating  together  benzoic  aldehyde,  sodium  acetate,  and 
acetic  anhydride  (Perkin's  reaction)  :  — 

H  H 

C6H5 .0:0  +  HCH2 .  C02Na  =  C6H5  -  0  -  OH. 

I 
CH2-C02Na 

The  acetic  anhydride  acts  as  a  dehydrating  agent  and  con- 
verts the  product  first  formed  into  sodium  cinnamate :  — 

H 
C6H5 .  C  -  OH         =  G^  CH  .  CH  co^  +  ^ 

CH2.C02Na 

3.  By  treating  benzal  chloride  with  sodium  acetate :  — 
C6H5 .  CH|C12:  +  CjH2jH. C02Na=C6H5.  CH :  CH .  C02Na+2  HC1. 
C6H6 .  CH :  CH .  C02Na  +  HC1  =  C6H5 .  CH :  CH .  C02H  +  NaCl. 

The  acid  has  been  manufactured  on  the  large  scale  by  the 
last  method. 

Cinnamic  acid  is  a  solid  which  crystallizes  in  monoclinic 


378         HYDROCARBONS,    C^H^^   AND    DERIVATIVES 


prisms.     It  melts  at  133°,  and  boils  at  300°  to  400°.     It  is 
easily  decomposed  into  styrene  and  carbon  dioxide  :  — 

C6H5  .  CH  :  CH  .  C02H  =  C6H5  .  CH  :  CH2  +  C02. 

Oxidizing  agents  convert  it  first  into  benzoic  aldehyde  and 
then  into  benzoic  acid.  Nascent  hydrogen  converts  it  into 
hydro-cinnamic  or  phenyl-propionic  acid,  C6H5  .  CH2.  OH2.  CO2H 
(p.  333).  It  unites  with  hydrochloric,  hydrobromic,  and  hydri- 
odic  acids  :  — 

C6H5  .  C2H2  .  C02H  +  HC1  =  C6H5  .  C2H3C1  .  C02H. 

Phenyl-chlor-propionic  acid 

Bromine  yields  the  addition-product  C0H5  .  C2H2Br2  .  C02H. 
Treated  with  substituting  agents,  such  as  nitric  acid,  etc.,  it 
yields  substitution-products  in  which  the  entering  atoms  or 
groups  are  contained  in  the  benzene  residue,  in  the  ortho  and 
para  positions  relatively  to  the  acrylic  acid  residue,  C2H2.  C02H. 

Nitro-cinnamic  acids,  C6H4    °2?2   CO2H    _  The    orfcho 

' 


and  para  acids  are  formed  by  dissolving  cinnamic  acid  in  nitric 
acid. 

NOTE  FOR  STUDENT.  —  What  are  the  products  when  toluene  is  treated 
with  nitric  acid  ?  When  benzoic  acid  is  treated  in  the  same  way  ?  To 
which  case  is  the  above  analogous  ? 

(  C*  TT     f*O  TT 

Amino-cinnamic  acids,  C6H4  -j     -    *'    '    2     .  —  These  acids 

are  formed  by  treating  the  nitro-acids  with  reducing  agents. 
The  ortho  acid  loses  water  when  set  free  from  its  salts,  and  forms 

,CK  =  CH  ,CR  =  CH 

the  anhydride  carbostyril,  CftH  <Q  I      or  CfiH,<f  I 

4  \NH-CO  4\    N  =  C(OH) 

analogous  to  hydro-carbostyril  (p.  334). 


Coumarin,  C9H6O2(c6H4  JC^^°)>  is  a  compound  found 
in  Tonka  beans  and  in  many  other  plant  substances.      It  is 


COUMARIN  379 

made  synthetically  from  salicylic  aldehyde,  sodium  acetate,  and 
acetic  anhydride,  just  as  cinnainic  acid  is  made  from  benzoic 
aldehyde,  sodium  acetate,  and  acetic  anhydride.  The  first 
product  of  this  action  is  probably  ortho-hydroxy-dnnamic  acid, 

(  C*  TT      tf^OOIT 

or  coumaric  acid,  C6H4 1    2  ,  from  which,  by  treatment 

with  hydrobromic  acid,  coumarin  is  formed.  This  has  a  pleas- 
ant odor,  like  that  of  sweet  clover,  and  is  used  in  perfumery. 
In  very  great  dilution  it  has  the  odor  of  new-mown  hay. 
Treated  with  bases,  it  yields  salts  of  coumaric  acid. 

The  coumaric  acid  made  artificially  is  the  trans  variety,  that 
is  to  to  say,  the  one  that  has  the  hydroxyl  and  carboxyl  groups 
on  the  opposite  sides  of  the  molecule  as  represented  in  the 

H  -  C  —  C6H4OH 

formula,  n  .   Treatment  with  hydrobromic  acid 

H02C-C-H 

H-C-C6H4OH 
transforms  this  into  the  ds  variety,         n  ,  which  then 

H  -  C  -  C02H 
H-C-C6H4V 

loses  water,  forming  coumarin,         n  >0. 

H-C-CO   ' 


CHAPTER   XVIII 
PHENYL-ACETYLENE   AND  DERIVATIVES 

Phenyl-acetylene,  acetenyl-benzene,  C6H5.C:CH,  bears 
to  acetylene  the  same  relation  that  styrene,  or  phenyl-ethylene, 
bears  to  ethylene.  It  is  made  from  styrene  in  the  same  way 
that  acetylene  is  made  from  ethylene :  — 

(1)  C2H4  +  Br2        =C2H4Br2; 

(2)  C2H4Br2  +2KOH  =  C2H2  +  2KBr  +  2H20. 
C6H5 .  C2H3       -f-  Br2        =  C6H5 .  C2H3Br2 ; 

C6H5 .  C2H3Br2  +  2  KOH  =  C6H5 .  C2H  +  2  KBr  +  2  H20. 

Phenyl-acetylene 

It  is  a  liquid  that  boils  at  142°.  It  unites  directly  with  four 
atoms  of  bromine,  forms  metallic  derivatives,  and,  in  general, 
conducts  itself  like  acetylene  (which  see). 

Phenyl-propiolic  acid,  C9H6O2(C6H5 .  CiC .  CO.H).  —  This 
acid  is  a  carboxyl  derivative  of  phenyl-acetylene,  bearing  to  it 
the  same  relation  that  ciimamic  acid  bears  to  phenyl-ethylene. 
It  is  made  from  cinnamic  acid,  by  treating  the  dibroinine  addi- 
tion-product with  alcoholic  potash.  The  reaction  takes  place 
in  two  stages :  — 

C6H5 .  CHBr .  CHBr  .  C02H  =  C6H5 .  CH :  CBr .  C02H  +  HBr ; 
C6H5 .  CH  :  CBr .  C02H  =  C6H,  .0:0.  C02H  +  HBr. 

It  forms  long  needles,  which  melt  at  136°  to  137°.  When 
heated  with  water  to  120°,  it  breaks  up  into  carbon  dioxide  and 
pheny  1-acety  lene . 

380 


INDIGO   AND    ALLIED   COMPOUNDS  381 

Ortho-nitro-phenyl-propiolic  acid,   C6H4j     2          2    ,   is 

(  NO2(0) 

made  from  the  dibromide  of  ortho-nitro-cinnamic  acid,  in  the 
same  way  that  phenyl-propiolic  acid  is  made  from  the  dibromide 
of  cinnamic  acid  (see  preceding  paragraph).  It  is  of  special 
interest,  for  the  reason  that  it  can  easily  be  transformed 
into  indigo.  The  transformation  is  most  readily  effected  by 
boiling  it  with  alkalies  and  grape  sugar,  or  some  other  mild 
reducing  agent.  The  reaction  is  represented  by  the  following 
equation:  — 

2  C6H,        •  CO«H  +  H4  =  C16HIONA  +  2  C02  +  2  H2O. 


2(0)  Indigo 

Ortho-nitro-phenyl- 
propiolic  acid 

INDIGO  AND  ALLIED  COMPOUNDS 

Indigo  is  the  oldest  dye  known.  A  mummy  cloth  4000 
years  old  has  been  shown  to  be  dyed  with  it.  The  value 
of  the  world's  annual  production  of  this  dye  is  estimated  at 
$20,000,000.  Until  recently  all  the  indigo  used  was  made 
from  the  indigo  plants,  but  most  of  that  now  used  is  manu- 
factured by  synthetical  methods. 

In  several  plants,  Indigofera  tinctoria,  Isatis  tinctoria,  etc., 
there  occurs  a  glucoside,  indican,  which,  under  the  influence  of 
dilute  mineral  acids  or  certain  enzymes,  breaks  up,  yielding  a 
member  of  the  glucose  group  and  a  substance  which  by  oxida- 
tion is  converted  into  indigo-blue.  The  indigo  of  commerce 
was  formerly  all  prepared  in  the  East  and  West  Indies,  in 
South  America,  Egypt,  Bengal,  and  other  warm  countries.  In 
brief,  the  process  is  this  :  — 

At  the  proper  stage  the  plants  are  cut  off  down  to  the  ground, 
put  in  a  large  tank,  and  covered  with  water.  Enzyme  action 
takes  place,  the  indican  breaking  up  and  yielding  indoxyl 
(which  see),  as  above  stated.  The  liquid  becomes  green,  and 
then  blue.  When  the  fermentation  is  finished,  the  liquid  is 


382  PHENYL-ACETYLENE   AND   DERIVATIVES 

drawn  off  into  a  second  tank.  This  liquid  contains  indigo- 
white  or  possibly  indoxyl  in  solution.  In  contact  with  the  air 
it  is  oxidized,  forming  indigo,  which,  being  insoluble,  is  thrown 
down.  In  order  to  facilitate  the  precipitation  of  the  indigo, 
the  liquid  is  thoroughly  stirred.  Finally,  the  liquid  is  drawn 
off,  the  precipitated  indigo  pressed  and  dried,  and  then  sent 
into  the  market. 

The  substance  prepared  as  above  has  a  dark-blue  color,  and 
contains  other  coloring  matters  besides  indigo-blue.  Its  value 
depends  upon  the  amount  of  the  definite  compound,  indigo-blue, 
contained  in  it. 

Indigo-blue,  indigotin,  C16H10N2O2.  —  Indigo-blue  is  ob- 
tained from  commercial  indigo  by  reducing  it  to  indigo-white, 
and  then  exposing  the  clear  colorless  solution  to  the  air,  when 
indigo-blue  is  precipitated. 

Experiment  78.  Into  a  test-tube  put  a  small.  quantity  of  powdered 
indigo  ;  add  fine  zinc  filings  or  zinc  dust  and  caustic  soda.  When  the 
mixture  is  heated  the  solution  becomes  colorless.  When  this  result  has 
been  reached,  pour  some  of  the  solution  into  a  small  evaporating  dish. 
Contact  with  the  air  colors  it  blue. 

Indigo-blue  can  be  made  artificially  by  a  number  of  methods, 
among  which  the  two  following  are  the  principal  ones  :  — 

1.  By  boiling  ortho-nitro-phenyl-propiolic  acid  (which  see) 
with  an  alkali  and  grape  sugar. 

2.  From  ortho-amino-benzoic  (anthranilic)  acid  by  treating 
it  with  chlor-acetic  acid  and  fusing  the  product  thus  obtained 
with  caustic  potash  :  — 


(1)  C6H,  <  +  C1CH2  .  Co2H  =  C6H, 

+  HC1; 

/9\         P  TT   ^NH.CH2.COOH  p  TT      .  NH  n     ^/^/-^TT 

(2)  CeH«<COOH  =C6H4<COH>C.COOH 

+  H20; 

(3)  C6H4<          >C.COOH         =CeHt<™  H 


INDIGO- WHITE  383 

The  compound  of  the  formula  C6H4<^"?>CH   is  called 

COIl 

mdoxyL     When  oxidized  by  air  in  alkaline  solution  this  is  con- 
verted into  indigo-blue :  — 


+  2H20. 

This  method  is  now  used  on  the  large  scale  very  successfully. 
The  anthranilic  acid  is  prepared  from  phthalic  anhydride, 
which  is  obtained  from  naphthalene  by  oxidizing  it  with  con- 
centrated sulphuric  acid  in  the  presence  of  a  little  mercury. 
The  conversion  of  phthalic  anhydride  into  anthranilic  acid  is 
effected  by  means  of  Hofmann's  reaction  (see  Anthranilic  acid 
and  Methylamine).  The  history  of  the  attempts  to  prepare 
indigo  synthetically  is  full  of  interest.  At  present  the  artifi- 
cially prepared  product  is  driving  natural  indigo  out  of  the 
market. 

Indigo-blue  crystallizes  from  aniline  in  dark-blue  crystals. 
It  sublimes  in  rhombic  crystals.  Its  vapor  has  a  purple-red 
color.  It  is  insoluble  in  water,  alcohol,  and  ether ;  soluble  in 
aniline  and  chloroform.  Oxidizing  agent-  Convert  it  into  isa- 
tine  (which  see).  Heated  with  solid  caustic  potash,  it  yields 
carbon  dioxide  and  aniline;  boiled  with  a  solution  of  caustic 
potash  and  finely  powdered  manganese  dioxide,  it  is  converted 
into  ortho-amino-benzoic  acid  (anthranilic  acid). 

Indigo-white,  C16H12N2O2,  is  formed  by  reduction  of  indigo- 
blue,  as  above  described.  Its  solutions  in  alkalies  rapidly  turn 
blue  in  the  air,  in  consequence  of  the  formation  of  indigo-blue. 

When  indigo  is  oxidized  with  nitric  acid,  isatine, 
is  formed :  — 


C16H10N A  +  02  =  2  C6H4  <         >  CO. 


384  PHENYL-ACETYLENE   AND   DERIVATIVES 

When  isatine  is  treated  with  sodium  amalgam,  it  takes  up 
hydrogen,  and  yields  dioxindol,  C8H7N02  :  — 


Isatine  Dioxindol 


By  further  reduction,  dioxindol  loses  an  atom  of  oxygen,  yield- 
ing oxindol,  C8H7NO  :  — 


CO  +  H2  =  C6H4  <         >  CO  +  H20. 

Dioxindol  Oxindol 

By  distilling  oxindol  with  zinc  dust,  iridol  is  formed  :  — 


Indol 

Constitution  of  indigo,  —  The  constitution  of  indigo  is  de- 
duced from  a  consideration  of  a  number  of  facts.  In  the  first 
place,  its  vapor  density  shows  that  it  has  the  molecular  weight 
represented  by  the  formula  C16H10]Sr202. 

CO 
Its  relations  to  isatine,  C6H4<^.     >CO,  make  it  probable 

that  indigo  contains  two  groups,  C6H4  <  -^  >  C  :  ,  united.     It 

can    be    made,   for  example,   by    reducing    isatine   chloride, 

CO 
C6H4<        >CC1,  a  reaction  that  can  be  most  readily  inter- 

preted thus  :  — 


+2  HC1. 
Further,   indigo  can  be  made  from  di-o-nitro-di-phenyl-di- 

r\  —.  ri  _  r\  _  r\ 

acetylene,  C6H4  <  ^^  ~  ^  >  C6H4,  a  fact  that  shows  that 

the  union  between  the  two  halves  of  the  indigo  molecule  is 
between  carbon  atoms.     The  presence  of  two  imino  groups  is 


METHYL-INDOL  885 

shown  by  introducing  radicals,  and  then  decomposing  the 
ethers  thus  formed.  It  is  found  that  the  radicals  are  given 
off  in  combination  with  nitrogen  in  the  form  of  substituted 
ammonias. 

All  these  facts,  and  all  others  that  have  been  established  by 
the  investigations  on  indigo,  are  in  harmony  with  the  view 
expressed  by  the  formula  for  indigo  already  given  :  — 


Indol,  C8H7N(c6H4<^>CHV  —  The  mother  substance 

of  indigo  and  related  compounds  is  indol.     As  stated  above,  it 
is  formed  from  oxindol  by  heating  it  with  zinc  dust.     It  is  also 


formed  from  ortho-amino-chlor-styrene,  C6H4  <        2  by 

v    .     ,.         n  i     -,      T1     .        •-,  CH  =  CHC1, 

elimination  of  hydrochloric  acid  :  — 


It  is  a  crystalline  substance  of  peculiar  odor. 
p-Methyl-indol,  skatol,  C6H4<^H>CHa.—  This  occurs  in 

CH3 
P 

human  faeces  and  is  largely  responsible  for  the  characteristic 
penetrating  odor  of  the  faeces. 


CHAPTER   XIX 

HYDROCARBONS  CONTAINING  TWO  BENZENE   RESIDUES 
IN  DIRECT  COMBINATION 

JUST  as  the  marsh-gas  residue,  methyl,  CH3,  unites  with  methyl 

CH3 
to   form  ethane,    I     >  so  the  benzene  residue,  phenyl,  C6H5, 

CH3  C6H5 

unites  with  phenyl  to  form  the  hydrocarbon  diphenyl,  I       ,  and 

C6H5 

residues  of  toluene  and  of  the  higher  members  of  the  series 
unite  in  a  similar  way  to  form  homologues  of  diphenyl. 

Diphenyl,  C12H10(C6H5.C6H5).  — This  hydrocarbon  is  made 
by  treating  brom-benzene  with  sodium :  — 

2  C6H5Br  +  2  Na  =  C12H10  +  2  NaBr ; 

and  by  conducting  benzene  through  a  tube  heated  to  redness :  — 
2  C6H6  =  C12H10  -f  H2. 

It  forms  large,  lustrous  plates.  It  melts  at  70.5°,  and  boils 
at  254°.  It  is  easily  soluble  in  hot  alcohol  and  ether. 

Diphenyl  is  an  extremely  stable  substance.  It  resists  the 
action  of  ordinary  oxidizing  agents,  but  with  strong  ones  it 
yields  benzoic  acid.  A  large  number  of  derivatives  of  diphenyl 
have  been  studied. 

Substitution-products  of  diphenyl.  —  Substituting  agents,  as 
the  halogens,  nitric  and  sulphuric  acids,  act  upon  diphenyl 
much  in  the  same  way  as  they  do  upon  toluene.  Of  the  mono- 
substitution-products,  three  varieties,  ortho,'  meta,  and  para, 
are  possible.  Of  these  the  para  derivatives  are  most  easily 
obtained  by  direct  action.  At  the  same  time  ortho  derivatives 


BENZIDLNE  387 

are  formed  to  some  extent.  By  further  action  ortho-para 
products  and  di-para  products  are  formed.  In  the  latter  the 
substituting  atoms  or  groups  occupy  the  positions  indicated 
below  :  — 

H    H  H    H 

C      C  C      C       .. 


CO  CO 

H    H  H    H 

C6H4.NH2(p) 
Benzidine,  I  .  —  This  is  dipara-diamino-diphenyl. 

C6H4.NH2(P) 

It  is  formed  by  reduction  of  dinitro-diphenyl,  and  also  by  the 
reduction  of  nitro-benzene  in  alkaline  solution.  In  the  latter 
case  hydrazobenzene,  which  is  isomeric  with  benzidine,  is  first 
formed,  and  this  is  then  transformed  into  benzidine  in  the 
presence  of  acids  (see  hydrazobenzene).  See  p.  296  :  -^ 

C6H5.NH  C6H4.NHa 

I         —  •*-     I 
•C6H5.NH  C6H4.NH2 

Hydrazobenzene  Benzidine 

Benzidine  is  manufactured  on  the  large  scale  by  this  method. 
It  is  a  solid  that  melts  at  122°. 

The  amino  groups  are  in  the  two  para  positions  in  benzidine. 

Benzidine  dyes.  —  Benzidine,  being  an  amino  derivative  of  an 
aromatic  hydrocarbon,  is  readily  diazotized,  and  the  final  prod- 
uct of  the  action  of  nitrous  acid  is  a  compound  containing  two 
diazo  groups  or  a  tetrazo  compound.  Thus  the  chloride  gives 
a  tetrazo  chloride  :  — 

C6H4.NH8.HC1  C6H4.N2C1 

I  —  >•     I 

C6H4.NH2.  HC1  C6H4.  N2C1 

The  tetrazo  compound  reacts  with  great  ease  with  aromatic 


388      HYDROCARBONS   WITH   TWO   BENZENE   RESIDUES 

amino-sulphonic  acids,  hydroxy-acids,  and  phenol-sulphonic 
acids,  forming  valuable  dyes  that  have  the  power  to  unite 
directly  with  cotton.  They  are  called  substantive  dyes.  The 
first  dye  of  this  kind  that  came  into  use  was  known  as  Congo 
red.  This  is  made  by  treating  diphenyltetrazonium  chloride 
with  sodium  naphthionate.  Naphthionic  acid,  as  will  be  shown 
further  on,  is  a  derivative  of  naphthalene  (see  below). 

Chrysamin  G.  is  made  by  the  action  of  sodium  salicylate  on 
diphenyltetrazonium  chloride  :  — 


6K 

Carbazol,   I        )NH,  is  a  curious  derivative  of  diphenyl 

C6H/ 

that  is  found  in  coal  tar  in  small  quantity.  It  has  been  shown 
to  be  a  substituted  ammonia  containing  a  residue  of  diphenyl. 
It  is  properly  designated  by  the  name  diphenyl-imide,  and  is 
represented  by  the  above  formula.  It  has  been  made  syn- 

(  C*  TT 

thetically  by  passing  the  vapor  of  diphenylamine,  NH\C6H5> 

through  a  red-hot  tube,  a  reaction  taking  place  which  is  analogous 
to  that  mentioned  above  as  taking  place  when  benzene  is  treated 
in  the  same  way,  the  product  in  the  latter  case  being  diphenyl. 

Naphthalene,  Ci0H8.  —  While  the  relations  of  diphenyl  to 
benzene  are  clearly  shown  by  its  simple  synthesis  from  brom- 
benzene,  the  relations  of  naphthalene  to  benzene  have  been 
discovered  through  a  careful  study  of  its  chemical  conduct. 
The  facts  can  be  best  interpreted  by  assuming  that  the  mole- 
cule of  naphthalene  is  formed  by  the  union  of  two  benzene 
residues  in  such  a  way  that  they  have  two  carbon  atoms  in 
common,  as  represented  in  the  formulas 


NAPHTHALENE  389 

H  H 

HC-CH-C-CH-CH  HC/  \/  \!H 

I  I  |  and  |  |j  |      • 

HC-CH-C-CH-CH  HC^  /C^  ^CH 

H         H 

How  this  conception  was  reached  will  be  shown  below,  after 
the  properties  and  the  reactions  of  naphthalene  shall  have  been 
discussed. 

Naphthalene  is  a  frequent  product  of  the  heating  of  organic 
substances.  Thus,  it  is  formed  by  passing  the  vapors  of  alco- 
hol, ether,  acetic  acid,  volatile  oils,  petroleum,  benzene,  toluene, 
etc.,  through  red-hot  tubes ;  and,  also,  by  treating  ethylene  and 
acetylene  in  the  same  way.  It  is  therefore  found  in  coal  tar, 
and  in  gas-pipes  used  for  gas  made  by  heating  naphtha, 
gasolene,  etc.,  to  high  temperatures.  It  has  been  made 
synthetically :  — 

1.  By  treating  o-xylylene  bromide  with  the  di-sodium  com- 
puund  of  the  ethyl  ester  of  symmetrical  ethane-tetra-carboxylic 
acid;  saponifying  the  ester  thus  formed;  and  distilling  the 
silver  salt  of  the  resulting  acid:  — 

H 

C  CH.Br 

NaC(C02C2H5)2 
+ 


390      HYDROCARBONS    WITH   TWO    BENZENE    RESIDUES 


yCH2  -  C(C02C2H5)2  /CH2  -  C(C02H)2 

C6H/  I  _>.C6H/  | 

NCH2  -  C(C02C2H5)2  NCH2  -  C(C02H)2 

<H2  -  CH(C02H)  /CH  =  CH 

,  .    r<  TT  /  i 

I  —  >•  ^6H4\  I      • 

H2  -  CH(C02H)  XCH  =  CH 

2.  ~By    conducting    phenyl-butylene    bromide    over    heated 
lime  :  — 

<H=CH 
|     . 
H=CH 

3.  When      y-phenylisocrotonic      (phenylvinylacetic)     acid. 
C6H5.CH  =  CH.CH2.  COOH,  is  heated,  it  loses  water  and 
gives  a-naphthol,  a  hydroxyl  derivative  of  naphthalene  :  — 

H          H  H         H 

CO  CO 


C    H    CO  C 

H 


By  reduction  with  zinc  dust  a-naphthol  gives  naphthalene. 

The  above  syntheses  give  a  clew  to  the  constitution  of  naph- 
thalene, but  they  do  not  clear  it  up  entirely.  A  study  of  the 
chemical  conduct  of  naphthalene  has,  however,  led  to  a  solution 
of  the  problem. 

Naphthalene  is  prepared  on  the  large  scale  from  those  por- 
tions of  coal  tar  which  boil  between  180°  to  250°.  This  material 
is  treated  with  caustic  soda,  and  then  with  sulphuric  acid,  and 
distilled  with  water  vapor. 

It  forms  colorless,  lustrous,  monoclinic  plates.  It  melts  at 
80°,  and  boils  at  218°.  It  has  a  tarry  odor  ;  is  volatile  with 
steam,  and  sublimes  readily.  It  is  insoluble  in  water  ;  easily 


NAPHTHALENE  391 

soluble  in  boiling  alcohol,  from  which  it  can  be  crystallized. 
Oxidizing  agents  convert  it  into  phthalic  acid  (see  Exp.  73). 
On  the  large  scale  phthalic  acid  is  made  from  it  by  oxidizing 
with  sulphuric  acid,  as  has  already  been  stated.  It  is  used  as 
an  antiseptic  and  insecticide.  The  well-known  moth  balls,  for 
example,  are  made  of  naphthalene. 

The  ease  with  which  naphthalene  yields  phthalic  acid,  sug- 
gests that  the  hydrocarbon  is  probably  a  di-derivative  of  benzene 
containing  two  hydrocarbon  residues ;  such,  for  example,  as  is 

C  C*  TT 

represented  by  the  formula  C6H4  j  C2H*'  Such  a  substance,  how- 
ever, contains  unsaturated  paraffin  residues,  and  hence  ought 
readily  to  take  up  bromine,  hydrobromic  acid,  etc.  Bromine 
and  chlorine  are  indeed  taken  up  easily,  but  the  products  thus 
obtained  act  rather  like  the  addition-products  of  benzene  than 
the  addition-products  of  the  unsaturated  paraffins.  They  break 
up  readily,  and  yield  stable  substitution-products  of  naphtha- 
lene. 

We  have  seen  that  a  hydrocarbon  containing  a  benzene 
residue  and  an  unsaturated  paraffin  residue,  as,  for  example, 
styrene  or  phenyl-ethylene,  C6H5 .  C2H3,  and  phenyl-acetylene, 
C6H5 .  C2H,  when  treated  with  bromine  or  hydrobromic  acid, 
takes  them  up  as  readily  as  ethylene  and  acetylene,  and  this 
action  takes  place  before  substitution.  According  to  this, 
naphthalene  ought  to  take  up  bromine  and  especially  hydro- 
bromic acid  with  avidity  before  substitution  of  its  hydrogen 
takes  place. 

While  it  does  take  up  four  atoms  of  chlorine  or  of  bromine,  it 
does  not  take  up  hydrochloric  or  hydrobromic  acid,  a  fact  that 
makes  it  improbable  that  naphthalene  contains  unsaturated 
hydrocarbon  residues. 

C  f^   TT 

The  formula  C6H4  •{    2   2  and  similar  ones  being  thus  rendered 
I  C2H2 

extremely  improbable,  the  next  thought  that  suggests  itself  is 
that  the  two  groups  CjH,  may  be  united,  as  represented  in  the 


392      HYDROCARBONS    WITH    TWO    BENZENE   RESIDUES 

{CH.CH 
I .      Assuming,  further,  that  the  two  groups 
CH.CH 

are  united  to  two  carbon  atoms  of  the  benzene  residue  which 
are  in  the  ortho  relation  to  each  other,  we  may  write  this  same 
formula  thus  :  —  U 

HC/   \C-CH-CH 


HC> 


—  CH  —  CH 


H 
or,  what  is  the  same  thing,  — 

H          H 

HC/  \C/  \GH 

HCv       / 
XT 
H          H 

This  formula  represents  naphthalene  as  made  up  of  two 
benzene  residues  united  in  such  a  way  that  they  have  two 
carbon  atoms  in  common.  This,  as  has  been  stated,  repre- 
sents the  hypothesis  at  present  held  in  regard  to  the  structure 
of  naphthalene. 

As  regards  the  assumption  that  the  two  residues  are  united 
through  carbon  atoms  which  are  in  the  ortho  position  relatively 
to  each  other,  it  should  be  said  that  this  assumption  is  made 
because  phthalic  acid  is  the  product  of  oxidation  ;  and  the  facts 
already  considered  have  shown  that  terephthalic  acid  must  be 
represented  by  the  formula 

C02H 

HC/  \CH 


C08H 


NAPHTHALENE  393 

and  isophthalic  acid  by 

C02H 

HC/  \CH 

I  I 

HCv        ,CC02H 

C 

H 

and  hence,  in  terms  of  the  accepted  hypothesis,  the  third  pos- 
sible formula  must  be  given  to  phthalic  acid,  viz.,  — 

H 
HC/  \C.C02H 

H'  '         H* 

.CXc/C.C02H 

H 

Are  there  any  facts  besides  those  above  mentioned  which 
make  the  hypothesis  appear  probable  ? 

By  a  different  line  of  reasoning,  based  upon  other  facts,  the 
conclusion  is  reached  that  naphthalene  is  made  up  of  two  ben- 
zene residues  which  have  two  carbon  atoms  in  common,  and 
the  only  formula  that  represents  this  conception  is  the  one 
already  given.  The  facts  which  lead  to  this  conclusion  are  the 
following :  — 

When  nitro-naphthalene  is  oxidized  it  yields  nitro-phthalic 
acid.  This  shows  that  the  nitro  group  is  contained  in  a 
benzene  residue;  and  we  may  represent  it  by  the  formula 

r  r\  TT 

C6H3.NO2  4  C2H2 ,  the  oxidation  taking  place  as  indicated  thus :  — 
C6H3 .  N02 1  ^2  +  90  =  C6H3 .  N02  j  ^2^  -f  H20  +  2  C02. 


By  reducing  this  same  nitro-naphthalene,  amino-naphthalene 
is  obtained;  and,  when  this  is  oxidized,  phthalic  acid  is 
formed :  — 


394      HYDROCARBONS    WITH    TWO    BENZENE   RESIDUES 


These  two  reactions  show  (1)  that  the  part  of  nitro-naphtha- 
lene  in  which  the  nitro  group  is  situated  is  a  benzene  residue ; 
(2)  that  there  is  another  benzene  residue  in  the  compound  into 
which  the  nitro  group  has  not  entered. 

These  transformations  may  be  represented  thus :  — 

H      H 


H 

Nitro-naphthalene 


Nitro-phthalic  acid 


H 


CH 


H    NH2 

Amino-naphthalene 


H 

Phthalic  acid 


It  has  been  noticed,  also,  that  by  oxidation  of  a  naphthalene- 
sulphonic  acid,  both  sulpho-phthalic  and  phthalic  acid  itself 
are  obtained. 

It  follows,  from  these  facts,  that  naphthalene  is  made  up  of 
two  benzene  residues,  and  the  only  way  in  which  a  hydrocarbon 
of  the  formula  C10H8  can  be  thus  made  up,  is  by  having  two 
carbon  atoms  common  to  the  two  residues,  as  represented  in 
the  formula  already  given :  — 


DERIVATIVES   OF   NAPHTHALENE  395 


H  H 

CP 
,    \      >A\. 
HC/     NX      X5H 


HCv        /^\       / 
XX       XX 
H          H 

The  proof  just  given  for  this  formula  is  independent  of  any 
notions  regarding  the  ortho,  meta,  and  para  relations  in  ben- 
zene. As  phthalic  acid  is  the  product  of  oxidation,  it  follows 
that  the  carboxyl  groups  in  the  acid  must  bear  to  each  other 
the  relation  expressed  by  the  formula 

H 

HC/  \C-C02H 

I  I 

HCV      /C  -  C02H 


H 

and,  therefore,  that  in  all  ortho  compounds  the  substituting 
groups  bear  this  same  relation  to  each  other.  Hence,  by  start- 
ing with  the  above  formula  of  phthalic  acid,  —  and  to  this,  it 
must  be  remembered,  we  are  led  independently  of  any  facts 
connected  with  the  formation  of  the  acid  from  naphthalene,  — 
the  accepted  formula  of  naphthalene  follows  naturally. 

Derivatives  of  Naphthalene 

An  interesting  fact  that  has  been  discovered  by  a  study  of  the 
mono-substitution-products  of  naphthalene  is  this,  —  that  two, 
and  only  two,  varieties  have  been  obtained.  There  is  an  a-  and  a 
/2-chlor-naphthalene,  an  a-  and  a  /?-brom-naphthalene,  etc.,  etc. 
This  fact  is  quite  in  harmony  with  the  views  held  regarding  the 
constitution  of  naphthalene,  as  will  readily  be  seen  by  examin- 
ing the  formula  somewhat  more  in  detail.  There  are  two,  and 
only  two,  kinds  of  relations  which  the  hydrogen  atoms  bear  to 
the  molecule  ;  all  those  marked  with  an  a  being  of  one  kind, 
and  all  those  marked  with  a  ft  being  of  another  kind  :  — 


396      HYDROCARBONS   WITH  TWO   BENZENE   RESIDUES 

a  H         a  H 

Cp 
x     V        /    \ 

NX     xi 


aH          aH 

Here,  again,  a  problem  presents  itself  like  that  presented  by 
the  di-substitution-products  of  benzene.  The  theory  gave  us 
three  formulas,  and  three  compounds  are  known.  The  problem 
was  to  determine  which  formula  to  assign  to  each  compound. 
Here  we  have  two  formulas  for  two  broin-naphthalenes  and 
other  mono-substitution-products  of  naphthalene,  and  we 
actually  have  two  compounds ;  and  the  question  arises,  which 
of  the  two  formulas  must  we  assign  to  a  given  compound  ?  The 
method  adopted  is  simple,  and  can  be  explained  in  a  few  words. 
That  nitro-derivative  of  naphthalene  which  is  known  as  a-nitro- 
naphthalene  yields  nitro-phthalic  acid  by  oxidation ;  and  the 
relation  of  the  nitro  group  to  the  carboxyl  groups,  in  this  acid, 
has  been  determined.  It  is  expressed  by  the  formula, 

N02 

HC/  \C-C02H 

I  I 

HCv        xC-C02H 


C\c/ 


H 

Formula  I. 

while  the  formula  of  the  other  nitro-phthalic  acid  is 

H 

C-C02H 
^C-COaH* 
H 

Formula  II. 


AMINO-NAPHTHALENE  397 

As  a-nitro-naphthalene  yields  the  acid  of  formula  L,  it  fol- 
lows that  in  it  the  nitro  group  must  occupy  the  position  of  one 
of  the  hydrogen  atoms  marked  a  in  the  above  formula  for  naph- 
thalene. Those  substitution-products  of  naphthalene  which 
belong  to  the  same  series  as  a-nitro-naphthalene  are  called  a 
derivatives.  In  the  ft  compounds  the  substituting  group  or 
atom  must  occupy  the  place  of  one  of  the  hydrogen  atoms 
marked  ft. 

According  to  the  theory  in  every  case  in  which  the  two 
substituting  atoms  or  groups  are  the  same,  there  are  ten  di- 
substitution-products  of  naphthalene  possible.  For  example, 
there  are  ten  di-chlor-naphthalenes  possible.  All  ten  are  known 
and  no  more.  The  relations  between  the  two  substituting 
atoms  can  be  followed  by  the  aid  of  the  figure  below:  — 


The  numbers  mark  the  positions  of  the  eight  hydrogen  atoms 
in  naphthalene.  Two  substituting  atoms  or  groups  may  bear 
to  each  other  the  relations 

.1,2;  1,3;  1,4;  1,6;  1,6;  1,7;  1,8;  2,3;  2,6;  2,7. 

Further,  there  are  fourteen  tri-substitution-products  possible 
in  which  the  three  substituting  atoms  or  groups  are  the  same. 

TJiere  are  fourteen  tri-chlor-naphthalenes  possible  and  all  are 
known. 

a-Amino-naphthalene,  a-naphthylamine,  a-C10H7.NH2.— 

This  is  formed  by  the  reduction  of  a-nitro-naphthalene,  which 
is  the  chief  product  of  the  treatment  of  naphthalene  with  nitric 
acid  in  the  cold.  It  melts  at  50°.  It  is  also  formed  from  the 
corresponding  hydroxyl  compound,  a-naphthol,  by  heating  it 


398      HYDROCARBONS   WITH  TWO   BENZENE   RESIDUES 

with  the  ammonia  compound  of  zmc  chloride.  It  turns  red  in 
contact  with  the  air.  It  has  a  fecal-like  odor. 

P- Ammo-naphthalene,  p-naphthylamine,  P-C10H7.NH2»  is 
made  from  /3-naphthol  by  treating  it  with  the  ammonia  com- 
pound of  zinc  chloride.  It  melts  at  112°  and  has  no  odor. 

Several  of  the  sulphonic  acids  derived  from  the  naphthyl- 
amines  are  of  value  for  the  preparation  of  dyes. 

Naphthionic  acid,  1,  4-naphthylamine-sulphonic  acid. 

—  It  is  the  sodium  salt  of  this  acid  that  gives  Congo  red  when 
brought  together  with  diphenyltetrazonium  chloride  in  the 
presence  of  sodium  hydroxide  (see  Benzidine)  :  — 


ow^af2HCl. 

Congo  red  -"-2 

When  /3-naphthylamine  is  treated  with  sulphuric  acid,  four 
mono-sulphonic  acids  are  formed. 

Naphthols,  Ci0H7.OH.  —  Both  of  the  naphthols  occur  in 
coal  tar.  They  act  in  general  like  the  phenols,  though  the 
hydroxyl  group  reacts  more  readily  than  that  in  the  phenols. 
It  has  already  been  seen  that  the  amino  group  can  be  substi- 
tuted for  the  hydroxyl  group  of  the  naphthols.  The  naphthols 
are  made  by  fusing  the  corresponding  sulphonic  acids  with 
caustic  potash :  — 

C10H7.  S03K  +  KOH  =  C10H7.  OH  +  K2S03. 

Both  sulphonic  acids  are  formed  when  naphthalene  is  treated 
with  sulphuric  acid.  At  low  temperatures  (80°)  the  a-acid  is 


NAPHTHOLS  399 

the  chief  product.  At  higher  temperatures  (160°)  the  /?-acid 
is  formed  in  larger  quantity.  Indeed,  the  a-variety  is  converted 
into  the  /3-variety  when  heated  with  sulphuric  acid. 

The  synthesis  of  a-naphthol  by  heating  y-phenylisocrotonic 
acid  has  already  been  referred  to  (see  page  390). 

a-Naphthol  is  difficultly  soluble  in  water,  crystallizes  in  lus- 
trous needles,  and  melts  at  95°. 

(3-Naphthol  is  easily  soluble  in  water,  crystallizes  in  leaflets, 
and  melts  at  122°. 

Naphthol-sulphonic  adds.  —  Many  of  these  are  known,  and 
are  used  in  the  preparation  of  azo  dyes.  Thje  1,  4-naphthol- 
sulphouic  acid  is  the  one  principally  used. 

Among  the  azo  dyes  derived  from  naphthalene  the  following 
may  be  mentioned  :  — 

a-Naphthol  orange,  formed  by  the  action  of  a-naphthol  on  ben- 
zene-diazonium  sulphonate  in  alkaline  solution.  It  is  repre- 

sented  by  the  formula  C10H6<  W'80*1^4)  . 

Biebrich  scarlet,  made  from  diazoazobenzenedisulphonic  acid, 

|6  "      S03       ,  and  /3-naphthol.     This  dye  may  serve  as  an  ex- 
N2.C6H4.S03H 

ample  of  the  possibilities  presented  by  the  azo  compounds.  Its 
formula  is 

N"    C  "FT  ^  SQjH 
Cl°H6<OH          "NI-C.H..SO.H. 

fi-Naphthol  orange  is  formed  by  treating  benzene-diazonium 
sulphonate  (see  sulphanilic  acid)  with  /3-naphthol  in  alkaline 

solution.     Its  formula  is  d0H6  <       CH*  '  S°3Na  • 


Some  of  the  simpler  derivatives  of  naphthalene  are  used  as 
dyes.  Among  these  the  following  may  be  mentioned  :  — 

2,  4-Di-nitro-a-naphthol,  C10H5(N02)2OH,  which  is  used  in  the 
form  of  the  sodium  salt  under  the  name  of  Martins1  Yellow  ; 


400      HYDROCARBONS   WITH   TWO   BENZENE   RESIDUES 

f  (N02)2(2,  4) 
Di-nitro-naphtholsulphonic  acid,  Ci0H4  \  SO3H(7)       ,  which  in 

I  OH(1) 

the  form  of  the  sodium  salt  is  used  under  the  name  Naphihol 
Yellow  S. 


a-Naphtho-quinone,  C10H6O2.  — This  compound  is  obtained 
by  oxidizing  naphthalene  with  chromic  acid ;  also  by  oxidizing 
a-amino-a-naphthol  and  other  di-substitution-products  of  naph- 
thalene in  which  the  two  substituting  groups  are  in  the  1,  4 
position  relatively  to  each  other.  It  bears  to  naphthalene  the 
same  relation  that  ordinary  quinone  bears  to  benzene ;  that  is, 
it  is  naphthalene  in  which  two  hydrogen  atoms  are  replaced 
by  two  oxygen  atoms. 

It  forms  yellow  needles,  which  melt  at  125°.  Like  ordinary 
quinone,  it  is  volatile  with  water  vapor.  Sulphurous  acid  con- 
verts it  into  a-naphtho-hydro-quinone :  — 

C10H602  +  H2  =  C10H6(OH)2  (1,  4). 

NOTE  FOR  STUDENT.  —  Compare  with  the  action  of  reducing  agents  on 
ordinary  quinone. 

It  gives  a  dioxime  with  hydroxylamine. 

p-Naphtho-quinone,  Oi0H6O2.  —  This  quinone  is  formed  by 
oxidizing  /2-amino-a-naphthol  with  ferric  chloride.  When  re- 
duced with  sulphurous  acid  it  gives  1,  2-di-hydroxy-naphthalene. 
It  consists  of  red  needles  that  decompose  at  115-120°.  It  is 
inodorous  and  is  not  volatile.  While  in  a-naphtho-quinone  the 
two  oxygen  atoms  are  in  the  1,  4  (para)  position  to  each  other, 
as  they  are  in  ordinary  benzoquinone  (see  Quinone),  in  /3- 
naphtho-quinone  the  oxygen  atoms  are  ortho  to  each  other. 
a-Naphtho-quinone  in  general  resembles  ordinary  quinone; 
/?-naphtho-quinone  does  not.  The  formulas  of  the  two  naph- 
tho-quinones  are  here  given  :  — 


QUINOLINE  AND   ANALOGOUS   COMPOUNDS  401 

CHnCO  CHCCO 


H  H 

a-Naphtho-quinoDe   '  /3-Naphtho-quinone 

Di-hydroxy-naphtho-quinone,    doH^J  ,  is    a  dye 


known  by  the  name  naphthazarin,  on  account  of  its  resem- 
blance to  alizarin  (which  see). 

Homologues  of  naphthalene  —  like  methyl-  and  ethyl-naph- 
thalene —  have  been  prepared;  a-  and  ^-methyl-naphthalene 
have  been  found  in  coal  tar. 

QUINOLINE  AND  ANALOGOUS  COMPOUNDS 

When  quinine  or  cinchonine  is  distilled  with  caustic  potash, 
a  basic  substance  of  the  formula  C9H7N  is  formed.  This  is 
called  quinoline.  It  occurs  in  coal  tar  together  with  an  iso- 
meric  substance  iaoquinoline,  and  some  homologues.  Among 
the  compounds  homologous  with  quinoline  are  the  following  :  — 

Quinaldine,  a-Methyl-quinoline  ....  C10H9K. 
Lepidine,  y-Methyl-quinoline  ....  C10H9N. 
Cryptidine  ...  ........  CUHUN. 


Quinoline,  C9H7N.  —  Quinoline  is  formed  by  the  distillation 
of  quinine,  cinchonine,  or  strychnine,  with  caustic  potash;  is 
formed  from  certain  derivatives  of  benzene;  and  is  found  in 
coal  tar. 

1.   By  passing  allyl-aniline  over  heated  lead  oxide :  — 
C6H5.NH.CH: 


402      HYDROCARBONS    WITH   TWO   BENZENE   RESIDUES 

This  synthesis  is  similar  to  that  of  naphthalene  from  phenyL 
butylene  (see  p.  390). 

2.  By  heating  together  glycerol,  aniline,  nitro-benzene,  and 
sulphuric  acid.  In  this  case  acrolein  is  probably  first  formed 
from  the  glycerol  by  the  action  of  the  sulphuric  acid :  — 

CH2OH     CH2 

I  II 

CHOH  =  CH  +2H20. 

I  I 

CH2OH  CHO 

This  acrolein  then  combines  with  aniline  thus :  — 

H  H 

C     XNH2  C       ^v 


-rrr\/  \/~i 

HC,      C 

Hr1        r1 
\/ 


+  OHC.CH  =  CH2=  T     +H20. 

TTr\\          n~PT         PTT 
XlLiK       J\ji\.        ,\jJLL 

CH  CH   HC 

H 

The  nitro-benzene  now  acts  as  an  oxidizer,  and  removing  two 
hydrogen  atoms  gives  quinoline :  — 


CH  n  N 
H' 


HC 
H     H 


4-H20. 


The  nitro-benzene  in  acting  as  an  oxidizing  agent  is  itself 
reduced,  and  the  aniline  thus  formed  enters  into  reaction  to- 
gether with  the  other  aniline  present.  The  whole  change  can 
be  represented  as  below :  — 

2  C6H4NHa  -f  C6H6NOa  +  3  C3H ,0,  =  3  C9H7N  + 11  HaO. 


QUINOLINE   AND   ANALOGOUS   COMPOUNDS  403 

3.   From  o-amino-cinnamic  aldehyde  by  loss  of  water  :  — 

CH.CHO  /CH  =  CH 

=  C6H4 

N-CH 


/ 
C6H4/  =  C6H4  I 


or 


This  simple  synthesis  shows  very  clearly  the  constitution  of 
quinoline.  It  is  analogous  to  naphthalene  in  a  way.  Just  as 
the  latter  is  made  up  of  two  benzene  rings  united  by  two  com- 
mon carbon  atoms,  so  quinoline  is  made  up  of  a  benzene  ring 
and  a  pyridine  ring  united  in  the  same  way.  This  hypothesis 
is  in  harmony  with  all  the  facts  known  in  regard  to  quinoline. 

4.  Another  synthesis  of  quinoline  is  effected  by  starting  with 
hydrocarbostyril  (which  see).  When  this  is  treated  with  phos- 
phorus pentachloride  it  is  converted  into  dichlor-quinoline,  and 
by  reduction  with  hydriodic  acid  this  gives  quinoline  :  — 


/CHo. 
C6H4< 

XN  = 


Quinoline  is  a  colorless  liquid  with  a  penetrating  odor,  and 
is  a  powerful  antiseptic.  It  boils  at  239°.  Potassium  per- 
manganate converts  it  into  quinolinic  acid,  which  is  a  pyridine- 
dicarboxylic  acid,  C5H3N(C02H)2.  The  formation  of  this  acid  is 
analogous  to  the  formation  of  phthalic  acid  from  naphthalene:—* 


404      HYDROCARBONS   WITH   TWO   BENZENE    RESIDUES 

CH, 


It  has  already  been  pointed  out  that  quinolinic  acid  gives 
pyridine  when  distilled  with  lime  and  that  the  accepted  hypoth- 
esis in  regard  to  the  constitution  of  pyridine  is  based  on  this 
fact  and  the  formation  of  quinolinic  acid  from  quinoline  (see 
Pyridine). 

Quinoline  forms  well-characterized  salts  with  acids.  In 
these  salts  it  acts  like  a  mon-acid  base.  The  number  of  sub- 
stitution-products derivable  from  quinoline  is  large.  Thus 
there  are  seven  mono-substitution-products  possible,  as  will  be 
seen  by  an  examination  of  the  figure  below  :  — 

a) 

CHCN 


CH     CH 
(4)    (>) 

A  substituting  atom  or  group  may  take  the  place  of  any  one 
of  the  hydrogen  atoms  indicated  by  the  letters  a,  ft,  and  y,  and 
the  numbers  1,  2,  3,  4,  each  of  which  bears  a  different  relation 
to  the  nitrogen  atom.  According  to  tMs  there  are  seven  possi- 
ble mono-methyl  derivatives.  All  of  these  are  known.  So  also 
there  are  seven  possible  mono-chlor  derivatives,  and  all  of  these 
are  known. 

The  methyl  derivatives  are  designated  by  the  letters  a,  /?,  y, 
and  the  numbers  1,  2,  3,  4. 

a-Methyl-quinoline,  quinaldlne,  09H6(CH3)N.  —  This 
occurs  in  coal  tar,  and  can  be  made  by  digesting  aniline, 
paraldehyde,  and  hydrochloric  acid:  — 


HYDROXY-QUINOLINB  405 


C(CH8) 
and  by  treating  o-amino-benzoie  aldehyde  with  acetone  :  — 

/CHO     CH8  /CH  =  CH 

/  |  / 

CO-CH3 


C6H4/  +|  =  C6H4/  |  +  2H20. 

\NH       CO-CH  \  N  =  C-CH 


•y-Methyl-quinoline,  lepidine,  C9H6(CH3)N.  —  This  occurs 
together  with  quinoline  and  quinaldine  in  coal  tar,  and  it  is 
formed  by  distilling  cinchonine  with  caustic  potash.  When 
this  is  brought  together  with  iso-amyl  iodide  an  addition- 
product  is  formed,  and  when  the  latter  is  treated  with  caustic 
potash  the  substance  known  as  cyanin  is  formed  :  — 

2  C10H9N  .  C5HUI  =%C30H39N2I  +  HI. 

Cyanin  forms  monoclinic  prisms  with  a  metallic  green  lustre. 
Its  solution  in  alcohol  is  deep  blue.  This  color  is  destroyed 
by  acids  and  restored  by  alkalies. 

/  N=CH  . 

1-Hydroxy-quinoline.  CeHsCOHX'  ,  is  formed  from 

XCH=CH 

1-quinoline-sulphonic  acid  by  fusing  it  with  caustic  potash. 

a-Hydroxy-quinoline,  carbostyril,  is  formed  by  the  elimi- 
nation of  water  from  o-amino-cinnamic  acid.  It  has  either  the 
hydroxyl  or  the  keto  group  in  the  pyridine  ring  :  — 

CH     CH  CH  p  GH 

HC,^V\CH 


Hydrogen  addition-products  of  quinoline  and  its  derivatives.  — 
Quinoline,  like  naphthalene,  takes  up  hydrogen  quite  easily. 
Tin  and  hydrochloric  acid  convert  it  into  tetra-hydro-quinoline, 
in  which  the  hydrogen  has  been  added  to  the  pyridine  ring  :  —  • 


406      HYDROCARBONS    WITH   TWO    BENZENE   RESIDUES 

xCH2-CH2 

*\tf  H  -  CH2 

The  hydrochloride  of  1-hydroxy-methyl-tetra-hydro-quino. 
line  is  used  as  a  febrifuge  under  the  name  Jcairine. 

The  sulphate  of  4-methoxy-tetra-hydro-quinoline,  called  thai- 
line,  is  also  used  as  a  febrifuge. 

The  final  product  of  the  addition  of  hydrogen  to  quinoline 
is  deca-hydro-quinoline,.  CgH^N. 

CHCCH 
Isoquinoline,  .  —  A  base  isomeric  with  quino- 

CHCCH 

line  is  found  with  it  in  coal  tar.  This  base,  which  is  called 
isoquinoline,  can  be  made  by  methods  that  show  that  the 
isomerism  with  quinoline  is  due  to  a  difference  in  the  position 
of  the  nitrogen  atom.  In  it  the  nitrogen  atom  is  not  directly 
connected  with  the  benzene  ring,  but  it  is  in  the  /^-position  as 
shown  in  the  above  formula.  It  can  be  made,  for  example, 

C*  TT      f^OOT-T 

from  the  imide  of  an  acid  of  the  formula  C6H4<COQH 
(homophthalio  acid).     This  imide  has  the  formula 

/CH2-CO 
C6H4<(  | 

^CO  -  NH 

When  treated  with  phosphorus  oxychloride  it  gives  dichloiN 

/CH  =CC1 
isoquinoline,  C6H4/  |     ,  and  this  when  reduced  by  means 

^ccl  =  N  /CH  =  CH 

of  zinc  dust  gives  isoquinoline,  C6H4/  |     .     Isoquinoline 

melts  at  23°  and  boils  at  240.5°.  It  resembles  quinoline  in  its 
general  properties. 

Several  alkaloids  are  derivatives  of  tetra-hydro-isoquinoline, 
such,  for  example,  as  papaverine,  narcotine,  and  hydrastme. 


CHAPTER  XX 

HYDROCARBONS  CONTAINING  TWO  BENZENE   RESIDUES 
INDIRECTLY  COMBINED 

DIPHENYL  and  naphthalene  have  been  shown  to  consist  of  two 
benzene  residues  in  direct  combination.  Diphenyl-inethane  is 
an  example  of  a  hydrocarbon  consisting  of  two  benzene  resi- 
dues in  indirect  combination,  C6H5.CH2.  C6H5.  As  diphenyl- 
m  ethane  is  closely  related  to  toluene,  it  was  treated  of  in 
connection  with  the  hydrocarbons  of  the  benzene  series. 
There  are  some  hydrocarbons  which  have  been  shown  to  con- 
sist of  two  benzene  residues  united  by  means  of  residues  of 
unsaturated  paraffins.  The  most  important  of  these  is  the 
well-known  anthracene. 

Anthracene,  C14H10.  —  Anthracene  is  formed  under  condi- 
tions similar  to  those  which  give  rise  to  the  formation  of 
naphthalene,  especially  by  heating  organic  substances  to  a 
high  temperature,  and  is  hence  found  in  coal  tar. 

It  has  been  made  synthetically  from  benzene  derivatives  by 
a  number  of  methods  :  — 

1.    By  heating  ortho-brom-benzyl  bromide  with  sodium;  — 

{PTT  T£r 
-X    2      +  4  Na  =  C14H10  +  4  NaBr  +  2  H  ; 
I1r(o) 

r   (  CH2Br     Br         "> 
CH42 


/CH\ 
=  C6H4<  |      >C6H4  +  4  NaBr  +  2  H. 

X/ 


407 


408      HYDROCARBONS    WITH   TWO    BENZENE   RESIDUES 

2.  By  treating  a  mixture  of  benzene  and  acetylene  tetra- 
bromide  with  aluminium  chloride  :  — 

BrCHBr  /CHv 

C6H6+       |          +  C6He=C6H/|      >C6H4  +  4HBr. 
BrCHBr  \CH/ 

Anthracene  is  prepared  in  large  quantity  from  those  portions 
of  coal  tar  which  boil  between  340°  and  360°.  The  distillate 
is  redistilled,  and  that  which  distils  after  the  temperature  has 
reached  340°  is  treated  with  liquid  sulphur  dioxide  to  remove 
the  impurities.  When  pure  it  forms  laminae,  or  monoclinic 
plates,  showing  a  beautiful  blue  fluorescence.  It  melts  at  213°, 
and  boils  at  351°. 

Anthracene  takes  up  hydrogen,  forming  di-hydro-anthracene, 
C14H12,  and  hexa-hydro-anthracene,  C14H16.  It  takes  up  bromine 
and  chlorine,  forming  first  addition-products  and  then  substi- 
tution-products. 

Oxidizing  agents  convert  anthracene  into  anthra-quinone, 
C14H802,  just  as  they  convert  naphthalene  into  naphtho- 
quinone. 

The  formation  of  anthracene  from  ortho-brom-benzyl  bromide 
and  from  benzene  and  acetylene  tetrabromide  (see  above)  fur- 
nishes strong  proof  in  favor  of  the  view  that  anthracene  con- 
sists of  two  groups,  C6H4,  united  by  the  group,  C2H2;  thus, 
C6H4.  C2H2.  C6H4.  It  hence  appears  as  a  diphenylene1  deriva- 
tive of  ethane,  C2H2(C6H4)2,  analogous  to  diphenyl-e thane, 
C2H4(C6H5)3.  This  conception  may  also  be  expressed  thus:  — 

a  a 

H  H 


H  H 

a  a 


ANTHRAQUINONE  409 

This  is  the  formula  commonly  accepted  for  anthracene.  It  is 
in  harmony  with  a  large  number  of  facts,  and  has  been  an 
efficient  aid  in  investigations  on  anthracene  and  its  derivatives. 
The  Greek  letters,  a,  /?,  y,  show  the  three  different  positions  of 
the  hydrogen  atoms,  and  indicate  that  there  are  three  possible 
mono-substitution-products  of  anthracene. 


Anthraquinone,    Ci4H8O2    C6H4  <       >  C6H4  .  —  Anthra- 
quinone  is  formed 

1.   By  direct  oxidation  of  anthracene  :  — 


2.   By  distilling  calcium  benzoate  :  — 


C6H4  <  >  C"H<  ~  C"H4  <  CO  >  Cettt  +  2 


3.  By  treating  phthalic  anhydride  with  benzene  in  the 
presence  of  aluminium  chloride.  The  first  product  is  ortho- 
benzoyl-benzoic  acid  :  — 

C6H4<  ™  >  O  +  C6H6=  C6H4< 

Ortho-benzoyl-benzoic  acid 

The  ortho-benzoyl-benzoic  acid  thus  formed  is  converted  into 
anthraquinone  when  heated  with  phosphorus  pentoxide  :  — 

5 


>C6H4  +  H2O. 

4.   By  distilling  calcium  phthalate :  — 


CH]co;o       : 
CsH4(  ;cpo>    i 

Experiment  79.  —  Dissolve  5&  commercial  anthracene  in  220CC  hot 
glacial  acetic  acid.     Slowly  add  to  the  boiling  solution  508  chromic  acid 


410      HYDROCARBONS   WITH   TWO    BENZENE    RESIDUES 

in  50CC  acetic  acid  (50  p.  c.).     Boil  for  some  hours.     After  cooling,  add 
750CC  water  ;  filter  j  wash  ;  dry  ;  and  sublime. 

Anthraquinone  forms  rhombic  crystals,  melting  at  285°.  It 
sublimes  in  yellow  needles  ;  is  insoluble  in  water,  but  slightly 
soluble  in  alcohol  and  ether.  It  is  an  extremely  stable  com- 
pound, resisting  the  action  of  alcoholic  potash  and  oxidizing 
agents.  Fused  with  solid  potassium  hydroxide,  it  yields  ben- 
zoic  acid  :  — 

PO 

C6H4  <  r;  >  C6H4  +  2  KOH  =  2  C6H5  .  COOK. 

(u\J 

Reducing  agents  convert  it  successively  into  oxanthranol, 
C14H1002,  anthranol,  C14H100,  and  anthracene,  C14H10.  These 
changes  may  be  represented  thus  :  — 


,  +  H2  =  C6H4  <  c  >  C6H4  ; 

Oxanthranol 

C(OH) 

>  C6H4  +  H2  =  C6H4  <  I  >  C6H4  +  H20  ; 

CH 

Anthranol 

C6H4  <  >  C6H4  +  H2     =  C6H4  <  I      >  C6H4  +  H20. 

CH 

When  heated  with  zinc  dust,  it  yields  anthracene.  A  great 
many  derivatives  of  anthraquinone  have  been  made.  Among 
the  best  known  are  the  hydroxyl  derivatives,  some  of  which 
are  much-prized  dyes  and  are  manufactured  in  great  quantities. 

The  hydroxyl  derivatives  of  anthraquinone  can  be  made  by 
melting  either  the  bromine  derivatives  or  the  sulphonic  acids 
with  caustic  potash. 

DSd^oxy-anthraquinone,  }  CWVUO^O,  (OH),]- 

Alizarin  is  the  well-known  dye  that  was  originally  obtained 
from  madder  root.     The  substance  found  in  the  root  is  rube- 


ALIZARIN"  411 

rythric  add,  a  glucoside  of  the  formula  C^H^O^.  When  this 
is  treated  with  dilute  acids  or  alkalies  or  ferments,  it  is  decom- 
posed, yielding  alizarin  and  a  glucose :  — 

C«Ha014  +  2  H20  =  C14H804  +  2  C6H1206. 

Alizarin  Glucose 

It  is  formed  by  fusing  dichlor-  or  dibrom-anthraquinone  or 
the  sodium  salt  of  anthraquinone-monosulphonic  acid  with 
caustic  soda  and  potassium  chlorate :  — 

C14H702 .  S03Na  +  NaOH  +  0  =  C14H602  (OH)2  +  Na2S03. 

Alizarin  is  now  manufactured  from  anthracene  on  the  large 
scale,  and  large  tracts  of  land  that  were  formerly  used  for 
cultivating  madder  are  used  for  other  purposes. 

Experiment  80.  Dissolve  20s  anthraquinone  in  a  small  quantity  of 
(fuming  sulphuric  acid,  heating  gradually  to  260°.  Dissolve  the  product 
in  a  litre  of  water.  Neutralize  with  finely  powdered  chalk  ;  filter.  Pre- 
cipitate with  a  solution  of  sodium  carbonate  ;  filter  ;  and  finally  evaporate 
to  dryness.  The  salt  thus  obtained  is  impure  sodium  anthraquinone-mono- 
sulphonate.  In  an  iron  crucible  mix  10s  of  the  sulphonate,  40&  sodium 
hydroxide,  and  3s  potassium  chlorate,  and  heat  for  several  hours  at  165° 
to  175°.  The  formation  of  alizarin,  during  the  melting,  is  shown  by  the 
dark  purple  color  of  the  mass.  When  a  little  of  this  is  dissolved  in  water, 
it  should  form  a  beautiful  purple-red  solution.  Continue  the  melting  until 
the  mass  acts  in  this  way.  Dissolve  the  mass  in  Jl  to  I1  water,  and  acidify. 
Alizarin  is  thrown  down  in  brown  amorphous  flakes.  Filter  off,  dry,  and 
sublime  between  watch-glasses. 

Alizarin  forms  red  needles,  which  melt  at  289°.  It  dissolves 
in  alkalies,  forming  dark  purple-red  solutions.  When  heated 
with  zinc  dust,  it  yields  anthracene.  It  was  this  reaction 
which  gave  the  first  clew  to  the  nature  of  alizarin,  and  led, 
soon  after,  to  its  synthesis. 

The  two  hydroxyl  groups  in  alizarin  are  in  the  a  and  /?  posi- 
tions in  one  benzene  ring,  as  shown  in  the  formula 


412      HYDROCARBONS   WITH   TWO   BENZENE   RESIDUES 


CHCCOCC(OH) 

(OH) 


H 


H 


The  evidence  in  favor  of  this  view  is  this :  Alizarin  is 
formed  by  heating  pyrocatechol  and  phthalic  anhydride  with 
sulphuric  acid.  This  shows  that  the  two  hydroxyl  groups  are 
in  the  ortho  position  with  reference  to  each  other.  It  is  only 
necessary  to  show  that  one  of  the  hydroxyls  is  in  the  a  position 
to  make  the  evidence  complete.  A  second  di-hydroxy-anthra- 
quinone  known  as  quinizarin  is  formed  from  phthalic  anhydride 
and  hydroquinol.  In  quinizarin,  therefore,  the  hydroxyl  groups 
are  in  the  para  position  with  reference  to  each  other,  — 


CH^CO^C(OH) 

When  quinizarin  is  oxidized,  a  third  hydroxyl  group  is  intro- 
duced, and  purpurin,  a  trihydroxy-anthraquinone,  is  formed. 
The  same  is  true  of  alizarin.     It  follows  therefore  that  in 
alizarin  the  hydroxyl  groups  are  in  the  a  and  (3  positions :  — 
CH   CO   C(OH) 


CCOCC(OH) 

'(OH) 


ALIZARIN  413 

There  are  ten  possible  di-hydroxy-anthraquinones.  Nine  of 
these  are  known.  Those  in  which  the  hydroxyl  groups  are  in 
the  ortho  relation  to  each  other  are  highly  colored. 

SdrVanthraquinone, 

Purpurin  is  contained  in  madder  root,  and  is  therefore  found 
in  madder  alizarin.  It  can  be  made  by  melting  alizarin-sul- 
phonic  acid  with  caustic  potash,  by  melting  tri-bromanthra- 
quinone  with  caustic  potash,  and  also  by  oxidizing  alizarin  or 
quinizarin  with  manganese  dioxide  and  sulphuric  acid. 

It  dissolves  in  water,  forming  solutions  that  are  pure  red. 
With  alumina  mordants  it  gives  a  beautiful  scarlet  red. 

Anthrapurpurin,  isopurpurin,  C14H5O2(OH)3,  is  found  in 

artificial  alizarin.          

Phenanthrene,  Ci4H10,  which  is  isomeric  with  anthracene, 
is  also  found  in  the  higher  boiling  parts  of  coal  tar.  It  is 
found  further  in  "stupp,"  a  mixture  of  substances  obtained 
in  the  distillation  of  mercury  ores  in  Idria.  It  is  formed  from 
dibenzyl  and  from  o-ditolyl  by  passing  their  vapors  through 
red-hot  tubes:  — 


C6H4.CH 

>•  I 
C6H4.CH 

C6H4.CH3 

When  oxidized,  phenanthrene  is  converted  into  diphenic  acid 
which  has  been  shown  to  be  a  di-ortho  car  boxy  1  derivative  of 
diphenyl,  — 

C6H4.C02H 

I 

C6H4.C02H 

In  this  process  phenanthraquinone  is  formed  as  an  interme- 


414      HYDROCARBONS   WITH   TWO   BENZENE  RESIDUES 

diate  product.  This  bears  to  phenanthrene  the  same  relation 
that  anthraquinone  bears  to  anthracene.  The  facts  mentioned 
and  all  other  facts  known  in  regard  to  phenanthrene  make 
it  clear  that  this  hydrocarbon  is  made  up  as  shown  in  the 
formula 


s Xfj       p\ -S 

CHCH^     °CHCH 

It  is  a  derivative  of  diphenyl,  and  consists  of  three  benzene 
rings.  The  formation  of  phenanthraquinone  and  of  diphenic 
acid  by  oxidation  of  phenanthene  is  easily  explained  on  this 
assumption : 

CO   CO 
CH  C/ \C  CH 

CHO^OCH 

CH  CH  ^  U  CH  CH 

Phenanthraquinone 


CH  CH         CH  CH 

Diphenic  acid 


CHAPTER  XXI 

GLUCOSIDES,  ALKALOIDS,  ETC.  —  CONCLUSION 

UNDER  the  head  of  the  sugars,  reference  was  made  (see  p.  188) 
to  a  class  of  compounds  called  glucosides,  that  occur  in  plants. 
These  substances  break  down  under  the  influence  of  dilute 
acids  or  enzymes  into  some  variety  of  sugar  and  other  com- 
pounds. Thus,  salicin  breaks  down,  according  to  the  equation 

C6H4(OH)CH2(OC6HU05)  +  H20 
=  C6H1206  +  C6H4(OH)CH2OH 

Glucose  Salicylic  alcohol 

into  glucose  and  salicylic  alcohol,  the  alcohol  corresponding 
to  salicylic  acid.  Some  of  the  more  important  glucosides  are 
mentioned  below. 


JEsculin,  C15Hi6O19  +  l|  H2O,  occurs  in  the  bark  of  the 
horse-chestnut  tree  (jfisculus  liippocastanum).  It  breaks  down 
into  glucose  and  sesculetin  :  — 

C15H1609  +  H20  =  C6H1206  +  C9H604.      . 

JEsculin  Glucose  ^Esculetin 

Its  water  solution  shows  blue  fluorescence. 


Amygdalin,  C^H^NOn  +  3  H2O,  occurs  in  bitter  almonds  ; 
also  in  the  kernels  of  apples,  pears,  peaches,  plums,  cherries, 
etc.  With  emulsin,  an  enzyme  contained  in  the  aqueous  ex- 
tract of  almonds,  amygdalin  is  broken  down  into  benzoic  alde- 
hyde, hydrocyanic  acid,  and  glucose  :  — 

C20H27NOn  +  2  H20  =  C7H60  +  CNH  +  2  C6H1206. 
415 


416  GLUCOSIDES,    ALKALOIDS,    ETC. 

Arbutin,  C12H16O7,  and  Methyl-arbutin,  C13H18O7,  occur  in 
the  leaves  of  some  varieties  of  the  grape.  They  break  down 
into  glucose  and  hydroquinol  or  methyl-hydroquinol. 


Coniferin,  C^H^Og  +  2  H2O,  occurs  in  the  cambium  layer  of 
the  conifers.  It  breaks  down  into  glucose  and  coniferyl  alco- 
hol. It  yields  vanillin  when  oxidized,  and  was  at  one  time 
used  in  the  preparation  of  vanillin  on  the  large  scale. 

Helicin,  Ci3Hi6O7  +  H2O,  is  formed  by  the  action  of  nitrous 
acid  on  salicin  (which  see).  It  has  also  been  made  artificially 
by  mixing  an  alcoholic  solution  of  acetochlorhydrose  with  the 
potassium  compound  of  salicylic  aldehyde  :  — 

C6H7C105(C2H30)4  +  C7H502K  +  4  C2H6O 
=  C13H1607  +  KC1  +  4  C2H5.C2H302. 

Acetochlorhydrose  is  formed  by  heating  glucose  with  an 
excess  of  acetyl  chloride. 

Helicin  breaks  up  into  glucose  and  salicylic  aldehyde. 

Myronic  acid,  CioHi9NS2Oio,  is  found  in  the  form  of  the 
potassium  salt  in  black  mustard  seed.  When  treated  with 
myrosin,  which  is  contained  in  the  aqueous  extract  of  mustard 
seed,  potassium  myronate  is  converted  into  glucose,  allyl 
mustard  oil,  and  acid  potassium  sulphate:  — 

C10H18NS2010K  =  C6H1206  +  C3H5.  NCS  +  KHS04. 

Phloridzin,  C^H^O^,  is  a  crystalline  substance  found  in  the 
root  bark  of  fruit  trees.  It  yields  glucose  and  Phloretin, 
CjsH^Os,  which  gives  phloretic  acid,  C9H1003,  and  phloroglucinol 
(which  see). 

Salicin,  C13H18O7,  occurs  in  willow  bark,  and  in  the  bark 
and  leaves  of  poplars.  Its  decomposition  into  salicylic  alcohol 
and  glucose  has  been  referred  to  (see  preceding  page). 


ALKALOIDS    OF   PERUVIAN    BARK  417 

Saponin,  CnH2n_8Oi0,  is  found  in  soap  root  (Saponaria 
offlcinalis).  ,  Its  water  solution  forms  a  lather  like  that  formed 
by  soap. 

ALKALOIDS 

The  alkaloids  are  compounds  occurring  in  plants,  frequently 
constituting  those  parts  of  the  plants  which  are  most  active 
when  taken  into  the  animal  body.  They  are  hence  sometimes 
called  the  active  principles  of  the  plants.  Many  of  these  sub- 
stances are  used  in  medicine.  As  regards  their  chemical  char- 
acter, they  are  basic  in  the  sense  that  ammonia  is  basic  ;  they 
contain  nitrogen,  and  form  salts,  just  as  ammonia  does,  i.e.,  by 
direct  addition  to  the  acids.  These  and  other  facts  lead  to  the 
belief  that  the  alkaloids  are  related  to  ammonia  —  that  they 
are  substituted  ammonias.  It  has  been  shown  that  several-  of 
the  alkaloids  are  related  to  pyridine  (see  p.  351)  and  quinoline 
(see  p.  401).  Only  a  few  of  the  more  important  alkaloids  need 
be  mentioned  here. 

Alkaloids  of  Peruvian  Bark 

Quinine,  C2oH24N2O2  +  3  H2O.  —  This  valuable  substance  is 
obtained  from  the  outer  bark  of  the  Cinchona  varieties.  When 
oxidized,  it  yields  derivatives  of  pyridine.  In  view  of  the 
interest  connected  with  quinine,  the  discovery  of  its  relation 
to  pyridine  and  quinoline  has  led  to  a  large  number  of  investi- 
gations on  the  derivatives  of  these  two  bases,  and  it  is  probable 
that  in  time  it  will  be  possible  to  make  quinine  synthetically 
in  the  laboratory. 

The  salts  of  quinine  are  formed  by  direct  addition  of  the 
base  to  the  acids.  Examples  are 


Quinine  hydrochloride      .     Cao 

Quinine  nitrate  .     .     .    .     Cgff^A  .  KN"03  ; 

Quinine  sulphate     .    .    .     C.»H24N202.H2SOi,  etc.,  etc. 


418  GLUCOSIDES,    ALKALOIDS,    ETC. 


Cinchonine,  C19H22N2O,  Cinchonidine,  C^I^^O,  find 
other  bases  occur  with  quinine  in  Peruvian  bark, 

Cocaine,  C17H21NO4,  is  found  in  coca  leaves  (Erythroxylon 
coca}  .  It  melts  at  98°  and  is  levo-rotatory.  Its  hydrochloric 
acid  salt,  C17H21lSr04.HCl,  has  recently  come  into  prominence 
in  medicine,  owing  to  the  fact  that  it  is  a  powerful  anaesthetic. 

Nicotine,  Ci0Hi4N2,  occurs  in  tobacco  leaves  in  combination 
with  malic  acid.  Potassium  permanganate  converts  it  into 
nicotinic  acid,  which  is  one  of  the  possible  pyridine-monocar- 
bonic  acids. 

Atropine,  C17H23NO3,  is  found  in  many  varieties  of  Solanum 
together  with  hyoscyamine,  with  which  it  is  isomeric.  It  is 
produced  from  this  by  treating  it  with  alcoholic  potassium 
hydroxide.  Atropine  gives  tropine  and  tropic  acid  (which  see) 
when  boiled  with  baryta  water.  Tropic  acid  has  been  shown  to 
be  a-phenyl-hydracrylic  acid, 

CH2(OH)-CH-C02H. 

I 
C6H5 

Tropine,  C8H15NO,  the  basic  constituent  of  atropine,  has 
been  prepared  artificially. 

Alkaloids  of  Opium 

Opium  is  the  evaporated  sap  which  flows  from  incisions  in 
the  capsules  of  the  white  poppy  (Papaver  somniferum)  before 
they  are  ripe.  The  three  principal  alkaloids  contained  in 
opium  are  morphine,  codeine,  and  narcotine. 

Morphine,  C17H19NO3  +  H2O,  is  a  crystallizable  solid  which 
is  difficultly  soluble  in  water,  alcohol,  and  ether.  When  de- 
composed, it  yields  pyridine,  trimethylamine,  and  phenan- 
threne,  together  with  other  products.  It  is  important  as  a 
soporific. 


STRYCHNINE  419 

Codeine,  C18H2iNO3,  is  a  mono-methyl  derivative  of  mor- 
phine and  can  be  prepared  from  it.  Like  morphine  it  is  exten- 
sively used  in  medicine. 

Narcotine,  C22H23NO7,  has  been  shown  to  contain  three 
methyl  groups,  which  are  split  off,  as  methyl  chloride,  when 
the  substance  is  heated  with  hydrochloric  acid.  It  is  a  deriva- 
tive of  tetra-hydro-isoquinoline. 

Piperine,  C17H19NO3,  is  contained  in  black  pepper.  When 
treated  with  alcoholic  potash,  it  breaks  down  into  piperidine 
and  piperic  acid  :  — 

C17H19N03  +  H20  =  C5HnN  +  C12H1004. 

Piperidine        Piperic  acid 

Piperidine,  C5HuN,  which,  as  just  stated,  is  formed  by  the 
decomposition  of  piperine,  has  been  made  synthetically  by 
treating  pyridine  with  nascent  hydrogen  :  — 


Pyridine  Piperidine 

It  is  therefore  hexa-hydropyridine  (see  p.  353). 

Strychnine,  C2iH22N2O2,  and  brucine,  C23H26N2O4  +  4  H2<D, 
are  two  alkaloids  that  occur  in  nux  vomica.  Strychnine  is  a 
most  violent  poison. 

In  the  animal  body  occur  a  large  number  of  complicated  sub- 
stances, the  study  of  which,  at  this  stage,  would  hardly  be 
profitable.  Thus,  there  are  the  albumins,  caseins,  and  fibrin  ; 
the  coloring  matters  of  the  blood,  oxyhaemoglobin,  haemoglobin, 
etc.  A  knowledge  of  these  substances  is  of  great  importance 
for  physiology,  and  much  progress  has  been  made  in  this  field. 

The  study  of  the  composition  of  animal  substances,  such 
as  milk,  urine,'  etc.,  and  of  the  relations  of  the  chemical  sub- 
stances occurring  in  the  body  to  the  processes  of  life,  is  the 
object  of  physiological  chemistry.  Without  a  good  knowledge 
of  the  general  chemistry  of  the  compounds  of  carbon,  how- 
ever, the  subjects  treated  of  under  the  head  of  Physiological 
Chemistry  cannot  be  understood. 


420  GLUCOSIDES,    ALKALOIDS,   ETC. 

ALBUMINS,  ETC. 

The  albumins  form  the  most  important  part  of  the  organism. 
They  enter  into  the  composition  of  protoplasm  and  of  all  the 
nutritive  liquids  of  the  body.  They  are  for  the  most  part  pre- 
cipitated by  heat,  by  strong  mineral  acids  and  by  many  me* 
tallic  salts,  such  as  cupric  sulphate,  lead  acetate,  mercuric 
chloride ;  by  alcohol  and  tannic  acid.  With  sodium  hydroxide 
and  very  little  cupric  sulphate  they  give  a  violet  color.  This 
is  the  biuret-reaction  referred  to  on  page  221. 

The  different  varieties  of  albumin  have  approximately  the 
same  composition.  All  contain  carbon,  hydrogen,  oxygen, 
and  sulphur.  * 

Hydrolytic  agents  such  as  hydrochloric  or  sulphuric  acid, 
baryta  water,  potassium  hydroxide,  and  also  certain  enzymes, 
as,  for  example,  pancreas  enzyme,  break  down  the  albumins 
and  give  many  simpler  products,  prominent  among  which  are 
amino-jpids.  Several  of  these  products  have  been  treated  of 
in  the  proper  places.  Those  which  should  receive  special 
mention  are  r 

Glycine,  alanine,  ammo-valeric  acid,  leucine,  isoleucine, 
phenyl-alanine,  aspartic  acid,  glutamic  acid ;  serine,  tyrosine, 
cystine,  cysteine ;  diamino-valeric  acid  (ornithine),  diamino- 
caproic  acid  (lysine) ;  urea,  ammonia. 

The  ammo-acids  are  linked  together  in  the  albumins,  forming 
very  complex  molecules.  The  polypeptides  (which  see)  are 
intermediate  between  the  amino-acids  and  the  albumins. 

Peptones.  —  These  are  products  formed  by  the  action  of  the 
juices  of  the  stomach  (pepsin)  and  of  the  pancreas  enzyme  on 
the  albumins.  The  first  products  of  the  action  are  anti-  and 
hemi-albumose.  These  then  pass  over  into  peptone.  The  pep- 
tones are  easily  soluble  in  water,  and  are  not  coagulated  by 
heat.  Further,  they  are  not  precipitated  by  most  of  the 
reagents  that  precipitate  albumin.  The  peptones  appear  to  be 
closely  related  to  the  artificially  prepared  polypeptides  (see 
p.  226). 


INDEX 


Abietic  acid,  357. 
Acetamide,  211. 
Acet-amino-phenol,  308. 
Acetanilide,  289. 
Acetates,  60. 
Acetenyl-benzene,  380. 
Acetic  acid,   3,   55,   58, 
130. 

aldehyde,  47. 

anhydride,  61. 

ether,  61. 

Acetochlorhydrose,  416. 
Acetone,  3,  71. 
Acetones,  71. 
Aceto-nitrile,  89. 
Acetophenone,  346. 
Acetyl  bromide,  61. 

chloride,  61. 
Acetylene,  246. 

-dicarbonic  acid,  250. 
Acetyl-glycolic        acid, 
161. 

iodide,  61. 

oxide,  61. 

-urea,  221. 
Acid  amides,  205,  211. 

fuchsine,  368. 

imides,  216. 
Acids,  55. 

Alcohol,  157. 

Benzene,  321. 

Dibasic,  141,  334. 

Fatty,  38,  130. 

Hexabasic,  337. 

Hydro  xy-,  157. 

Oxy-,  157. 

Sulphonic,  77,  298. 

Tribasic,  154. 

Unsaturated,  238, 250. 
Aconitic  acid,  182,  245. 


Acrolei'n,  236. 
Acrose,  186,  191. 
Acrylic  acid,  165,  238. 

acid  series,  238. 

aldehyde,  236. 
Active  compounds,  127. 

principles,  417. 
Adipic  acid,  143,  184. 
Adonite,  154. 
^Esculetin,  415. 
^Esculin,  415. 
Alanine,  163,  208. 
Albumins,  419,  420. 
Alcohols,  35,  121. 

Acid,  157. 

Benzene,  315. 

Di-acid,  137. 

Hex-acid,  155. 

Hept-acid,  156. 

Mon-acid,  137. 

Monatomic,  137. 

Pent-acid,  154. 

Primary,  123 

Secondary,  122. 

Sulphur,  75. 

Tertiary,  126. 

Tetr-acid,  154. 

Tri-acid,  148. 

Unsaturated,  233. 
Aldehyde,  47. 

-alcohols,  186. 

ammonia,  49. 

hydrocyanide,  47. 
Aldehydes,  47,  129. 

Benzene,  318. 
Aldol,  191. 

condensation,  191. 
Aldoses,  186. 
Alizarin,  410. 
Alkaloids,  417. 
Allomucic  acid,  184. 
Alloxan,  225. 
421 


Allyl  alcohol,  234. 
-aniline,  401. 
isosulpho-cyanate, 

236. 

mustard-oil,  235. 
sulphide,  235. 
Allylene,  249. 
Aluminium  ethyl,  106. 
Amic  acids,  215. 
Amines,  96. 
Amino-acetic  acid,  160, 

207. 

-acids,  205,  420. 
-azo-benzene,  296. 
-benzene,  286. 
-benzoic  acids,  327. 
-cinnamic  acids,    378. 
-cinnamic      aldehyde, 

403. 

compounds,  99. 
-dibasic  acids,  211. 
-ethane,  99. 
-ethyl-sulphonic  acid, 

210. 

-formic  acid,  206. 
-hydrocinnamic   acid, 

334. 
-hydroxy-propionic 

acid,  209. 

-hydroxypurin,  226. 
-isobutylacetic     acid, 

209. 
-methyl-ethyl-propi- 

onic  acid,  209. 
-naphthalenes,  397. 
-naphthol,  400. 
-phenols,  308. 
-propionic  acid,  163, 

209. 

-propionic  acids,  2'  8. 
•succinamic     acid, 
215. 


422 


INDEX 


Amino-succinic        acid, 
174,    211. 

-sulphonic  acids,  210. 

-toluenes,  289. 
Ammonia  bases,  100. 
Ammonias,  substituted, 

96. 

Ammonium  cyanate,  86. 
Amygdalin,  318,  415. 
Amyl  alcohols,  126. 

valerate,  135. 
Amylene,  230. 
Analysis,  10. 
Anethol,  343. 
Angelic  acid,  238. 
Anhydrogeraniol,  361. 
Anilides,  289. 
Aniline,  286. 

blue,  369. 

dyes,  290,  368. 

salt,  288. 

Anisic  acid,  305,  343. 
Anisol,  305. 
Anthracene,  407. 
Anthranilic  acid,  327. 
Anthranol,  410. 
Anthrapurpurin,  413. 
Anthraquinone,         408, 
409. 

-sulphonic  acid,  411. 
Anti-albumose,  420. 
Antifebrine,  289. 
Antipyrine,  298. 
Antitartaric  acid,  180. 
Apple  essence,  135. 
Arabic,  gum,  204. 
Arabinoses,  185,  187. 
Arabite,  154. 
Arachidic  acid,  131. 
Arbutin,  416. 
Archil,  313.  [256. 

Aromatic      compounds, 
Arsenic  compounds,  104. 
Aseptol,  308. 
Asparagine,  215. 
Aspartic  acid,  174,  211. 
Aspirin,  341. 
Asymmetrical       carbon 

atom,  166. 
Atropine,  418. 
Azelaic  acid,  143. 


Azo-benzene,  296. 

-compounds,  296. 
Azoxy-benzene,  297. 

B 

Barbier  reactions,  106. 
Barbituric  acid,  223. 
Bassorin,  204. 
Beef  tallow,  153. 
Behenic  acid,  131. 
Benzal  chloride,  282. 
Benzaldoximes,  320. 
Benzene,  254,  255. 

-diazonium  salts,  290. 

-disulphonic  acid,  300. 

hexabromide,  257. 

hexachloride,  278. 

series,  254. 

-sulphonic  acid,  299. 
Benzidine,  296,  387. 

dyes,  387. 
Benzine,  111,  257. 
Benzoic  acid,  265,  321. 

aldehyde,  318. 

sulphinide,  331. 
Benzophenone,  346. 
Benzoyl-amino-acetic 
acid,  330. 

benzoic  acid,  409. 

bromide,  325. 

chloride,  325. 

cyanide,  325. 

-formic  acid,  326. 
Benzyl  alcohol,  316. 

chloride,  316. 

cyanide,  332. 

ethers,  317. 

salts,  317. 
Beverages,        alcoholic, 

42. 

Biebrich  scarlet,  399. 
Bitter-almond   oil,  282, 
Biuret,  221.  [318. 

Bivalent  radicals,  141. 
Boiling-point,  8. 
Bone  oil,  3,  350. 
Borneo  camphor,  359. 
Borneol,  359. 
Bornyl  chloride,  357. 
Brassy  lie  acid,  143. 


Brom-benzene,  279. 

-ethane,  30. 

-methane,  28. 

-naphthalenes,  395. 

-picrin,  312. 

-propionic  acids,  132. 

-protocatechuic   acid, 

345. 

Bromoform,  28. 
Brucine,  419. 
Butane,  21,  109,  115. 
Butanes,  115. 
Butanic  acids,  133. 
Butene,  230. 
Butter,  153. 
Butyl  alcohol,  125,  129. 

alcohols,  124. 
Butylene,  230,  233. 
Butyric  acid,  130,  133. 

acid  ferment,  133. 

acids,  133. 


Cacodyl,  104. 

chloride,  105. 

oxide,  105. 

Caffeine,  226.  [217. 

Calcium  cyanamide, 
Camphanes,  357. 
Camphene,  357. 
Camphor,  359. 

Artificial,  361. 

Borneo,  359. 
Cane  sugar,  197. 
Cantharene,  276. 
Caoutchouc,  358. 
Capric  acid,  130. 
Caproic  acid,  130. 
Caprylic  acid,  130. 
Caramel,  198. 
Carbamic  acid,  94,  206. 
Carbamide,  218. 
Carbamines,  90. 
Carbazol,  388. 
Carbides,  248.         [127. 
Carbinol       derivatives, 
Carbohydrates,  185. 
Carbolic  acid,  303. 
Carbonic  acid,  158. 
Carbon  suboxide,  146. 


INDEX 


423 


Carbonyl,  53. 
Carbostyril,  378,  405. 
Carboxyl,  65. 
Carvacrol,  310,  360. 
Casein,  419. 
Celluloid,  202. 
Cellulose,  200. 

nitrates,  201. 
Cerotic  acid.  131. 
Ceryl  alcohol,  128,  129. 
Cetyl  alcohol,  128,  129. 
Chlor-acetic  acids,  63. 
Chloral,  54. 

hydrate,  54. 
Chlor-benzene,  279. 

-benzoic  acid,  326. 

-benzyl  alcohol,  317. 

-ethane,  30. 

-formic  acid,  158. 
Chlorhydrin.  150. 
Chlor-methane,  25,  28. 

-naphthalenes,  395. 

-picrin,  102. 

-propionic  acids,  132. 
Chloroform,  28. 
Cholic  acid,  210. 
Chrysamine,  388. 
Cimicic  acid,  238. 
Cinchonidine,  418. 
Cinchonine,  418. 
Cinnamic  acid,  376. 

aldehyde,  376. 
Cinnamyl  alcohol,  375. 

chloride,  377. 
Citraconic  acid,  244. 

anhydride,  183,  245. 
Citrates,  183. 
Citric  acid,  182. 
Classification  of  carbon 

compounds,  17. 
Coal  tar,  3,  254. 
Cocaine,  418. 
Codeine,  419. 
Cod-liver  oil,  153. 
Collidine,  350. 
Collodion,  201. 
Colophony,  357, 
Combustion  process,  11. 
Congo  red,  388,  398. 
Coniferin,  416. 
Conines,  353. 


Constitution     of     com- 
pounds, 16. 
Constitutional  formulas, 

16. 

Conyrine,  353. 
Coumaric  acid,  379. 
Coumarin,  378. 
Cream  of  tartar,  178. 
Creatine,  217. 
Creatinine,  218. 
Creosote,  309. 
Cresols,  309. 
Crotonic  acid,  238,  239. 

acids,  239. 

aldehyde,  237. 
Cryptidine,  401. 
Crystal  violet,  368. 
Crystallization,  4. 
Cuminic  aldehyde,  319. 
Cuminol,  319. 
Cuminyl  alcohol,  318. 
Cyan-acetic  acid,  143. 

-amides,  216. 
Cyanates,  93. 
Cyanic  acid,  85. 
Cyanides,  82,  88. 
Cyanin,  405. 
Cyanogen,  80. 

chlorides,  85. 
Cyan-propionic        acid, 

146,  147. 

Cyanuramide,  216. 
Cyanuric  acid,  86,  221. 
Cymene,  255,  274. 
Cymogene,  111. 
Cy stein,  209. 
Cystine,  209. 


D 

Dahlia,  369. 

Deca-hy  d  ro-quinoline, 

406. 

Denatured  alcohol,  42. 
Dextrin,  204. 
Dextro  compounds,  135. 
Dextrose,  187. 
Di-acetamide,  213. 

-amino-diphenyl,  387. 
Diastase,  40.  200. 


Diazo-amino-benzene, 

296. 
-amino      compounds, 

295. 
-benzene  compounds, 

290. 
-benzene,    Potassium, 

294. 

Diazonium  salts,  290. 
Di-brom-benzene,  281. 
Dichlor-acetic  acid,  63. 

-ethanes,  31. 
Dichlorhydrin,  150. 
Dichlo  r-isoquino  line, 

406. 

-toluene,  282. 
Di-cyan-diamide,  216. 
Di-ethylene  derivatives, 

249. 

Di-ethyl-amine,  96. 
-glycol  ether,  138. 
-phosphine,  104. 
-phosphinic  acid,  104. 
-phosphoric  acid,  69. 
Diglycyl-glycine,  226. 
Dihy  d  ro-an  th  racene, 

408. 

-benzenes,  276. 
-toluene,  276. 
Dihydroxy-acids,  169. 
-anthraquinone,  410. 
-benzenes,  310. 
-benzoic  acids,  343. 
-dibasic  acids,  176. 
Dihydro-xylenes,  276. 
Dihydroxy-naphthoqui« 

none,  401. 
-purin,  225. 
Dihyd  roxy-succinic 

acids,  177. 
-toluene,  313. 
Diiodo-methane,  28. 
Dimethyl-acetylene, 

249. 

-amine,  97. 
-amino-azo-benzene 

sulphonate,  301. 
-aniline,  288. 
-carbinol,  128. 
-ethylene,  233. 
-ethyl-methane,  117. 


424 


INDEX 


Dimethyl-ketone,   71. 

-methyl  alcohol,  123. 

-phosphine,  104. 

-pyrocatechol,  311. 

-xanthine,  226. 
Dinitro-benzene,  285. 

-di-phenyl-di-acety- 
lene,  384. 

-naphthol,  399. 

-naphtholsulphonic 

acid,  400. 
Dioxindol,  384. 
Dioxy  acetone,  186. 
Dipentene,  356. 
Diphenic  acid,  413. 
Diphenyl,  386. 
Diphenyl-amine,  289. 

-amine  orange,  302. 

ether,  305. 

-imide,  388. 

-iodonium  hydroxide, 
280. 

ketone,  346. 

-methane,  362. 

-phthalide,  370. 

-tetrazonium        chlo- 
ride, 387. 
Dipropargyl,  252. 
Di-sodium  glycol,  138. 
Distillation,  5. 
Diterpenes,  355. 
Dodecane,  109. 
Drying  oils,  251. 
Dulcite,  156. 
Durene,  255. 
Dynamite,  153. 
Dyeing,  367. 
Dyes,  aniline,  368. 

benzidine,  387. 

substantive,  368,  388. 

tri-phenyl-methane, 
365. 


Emerald  green,  60. 
Emulsin,  415. 
Enzymes,  40. 
Eosin,  373. 
Erucic  acid,  238. 
Erythrite,  154. 
Erythritic  acid,  170. 


Erythrol,  154. 
Erythrose,  186. 
Esters,  38,  67. 
Ethanal,  47. 
Ethandiol,  137. 
Ethane,  21,  25,  109. 
Ethanic  acid,  58. 
Ethanol,  39. 
Ethanolic  acid,  160. 
Ethene,  230. 
Ether,  43. 

Ethereal  salts,  38,  67. 
Ethers,  42. 

Mixed,  46. 

sulphur,  76. 
Ethine,  246. 
Ethyl  acetate,  61,  69. 

-acetylene,  249. 

alcohol,  39,  129. 

-amine,  89,  96. 

-ammonium      nitrite, 
100. 

-benzene,  269. 

bromide,  39. 

butyrate,  134. 

carbamine,  90. 

carbinol,  128. 

chlor-carbonate,  158. 

ohlor-formate,  158. 

chloride,  30. 

cyanide,  88. 
Ethylene,  230,  231. 

alcohol,  137. 

bromide,  137,  232. 

chlorhydrin,  138. 

chloride,  32,  232. 

cyanide,  146. 

-dicarbonic  acids,  241. 

glycol,  137. 

lactic  acid,  165. 

series,  230. 

succinic  acid,  146. 
Ethyl-ethylene,  233. 

ether,  43. 

-glycol  ether,  138. 

glycolate,  161. 

-glycolic  acid,  161. 
Ethylidene  chloride,  32, 

51. 

d-Ethylidene-lactic 
acid,  163. 


i-Ethylidene-lactic 

acid,  163. 
Z-Ethylidene-lactic 

acid,  164. 
Ethylidene  succinic 

acid,  147. 
Ethyl  iodide,  30. 
isocyanide,  90. 
isosulphocynate,  94. 
-mercaptan,  75. 
-methyl  alcohol,  123. 
-mustard  oil,  94. 
nitrate,  69. 
-phenyl     ether,     292, 

305. 

phosphate,  69. 
phosphine,  104. 
phosphinic  acid,  104. 
phosphoric  acid,  69. 
sulphate,  69. 
sulphide,  76. 
-sulpho-carbamic 

acid,  94. 

-sulphonic  acid,  76, 77. 
-sulphuric    acid,     43, 

69. 
-urea,  221. 


Fats,  153. 
Fatty  acids,  38. 
Fehling's  solution,  189. 
Fermentation,  4,  39. 

Acetic  acid,  39. 

Alcoholic    or  vinous, 
39. 

Lactic  acid,  39. 
Ferments,  39. 

Unorganized,  40. 
Ferric  succinate,  Basic, 

147. 

Ferricyanides,  83. 
Ferrocyanides,  83. 
Fibrin,  419. 
Fire  damp,  24. 
Flashing-point,  112. 
Fluorescei'n,  372. 
Formal,  47. 
Formalin,  47. 


INDEX 


425 


Formic  acid,  55,  130. 

aldehyde,  47. 
Formo-nitrile,  89. 
Formula,  Constitutional, 
16. 

Determination  of,  12. 

Structural,  15. 
Fractional      crystalliza- 
tion, 4. 

distillation,  6. 
Friedel-Crafts    reaction, 

265,  363. 

Fructosazone,  194. 
d-Fructose,  190. 
i-Fructose,  190. 
Z-Fructose,  191. 
Fruit  sugar,  190. 
Fuchsine,  366.  [103. 

Fulminating      mercury, 
Fulminic  acid,  103. 
Fumaric  acid,  174,  241. 
Fusel  oil,  41,  121,  127. 

G 

Galactonic  acids,  172. 
Galactoses,  195. 
Gallic  acid,  345. 
Garlic  oil,  235. 
Gasoline,  111. 
Gelatin,  Explosive,  202. 

sugar,  207. 
Geranial,  356. 
Geranic  acid,  356. 
Geraniol,  361. 
Glacial  acetic  acid,  59. 
Gluconic  acids,  172. 
Glucosazone,  194. 
Glucose,  40,  187. 
Glucosides,  188,  415. 
Gly eerie  acid,  152,  170. 

aldehyde,  186. 
Glycerin,  148. 
Glycerol,  133,  148. 

esters,  152. 

nitrates,  152. 
Glycerose,  185. 
Glyceryl  tri-oleate,  240. 

tri-palmitate,  149. 

tri-stearate,  149. 
Glycine,  207. 
Glycocholic  acid,  207. 


Glycocoll,  160,  207. 
Glycogen,  204. 
Glycol,  137. 
salts,  138. 
Gly  colic  acid,  160. 
Glycolide,  161. 
Glycols,  138. 
Glycyl-glycine,  226. 
Gfyoxylic  acid,  176. 
Grape  sugar,  40,  187. 
Grignard          reactions, 

106. 

Guaiacol,  311. 
Guanidine,  217. 
Guanine,  226. 
Gulonic  acids,  172. 
Guloses,  196. 
Gums,  204. 
Gun  cotton,  201. 

H 

Haemoglobin,  419. 
Heavy  oil,  254. 
Helianthin,  301. 
Helicin,  416. 
Heliotropine,  345. 
Hemi-albumose,  420. 
Hemiterpenes,  356. 
Hempel  tube,  8. 
Hepta-naphthene,  275. 
Heptanes,  109. 
Heptene,  230. 
Heptoic  acid,  130. 
Heptose,  186. 
Heptyl  alcohols,  129. 
Heptylene,  230. 
Hexa-brom-benzene, 

278. 
Hexachlor-benzene, 

278. 

Hexadecane,  109. 
Hexahydro-anthracene, 
408. 

-benzenes,  275. 

-cymene,  355. 

-methyl-benzene,  255. 

-methylene,  275. 

-methyl-pararosani- 
line,  368. 

-naphthene,  275. 


-pyridine,  419. 

-toluene,  275. 

-xylene,  275. 
Hexane,  21,  109,  118. 
Hexanes,  118. 
Hexene,  230. 
Hexoic  acid,  130. 
Hexoses,  186,  187. 
Hexyl  alcohols,  129. 
Hexylene,  230. 
Hippuric      acid,       207, 

330, 

Hofmann's        reaction, 
214. 

violet,  369. 
Homology,  21. 
Homophthalic  acid,  406. 
Honey  stone,  337. 
Human  fat,  153. 
Hydracrylic  acid,  164. 
Hydrastine,  406. 
Hydrazines,  101,  297. 
Hydrazo-benzene, 

296. 

Hydrazones,  193. 
Hydrocarbons,  18. 
Hydro-carbostyril,  334. 

-cinnamic  acid,  338. 
Hydrocyanic  acid,  81. 
Hydrolysis,  196. 
Hy  d  ro-naph  thoqui- 

none,  400. 
Hydroquinol,  312. 
Hydrosorbic   acid,   238, 

251. 

Hydroxy-acetic  acid, 
160. 

acids,  157. 

-benzoic  acids,  337. 

-butyric     aldehyde, 
191. 

-cinnamic  acid,  379. 

-dibasic  acids,  172. 

-ethyl-sulphonic  acid, 
167. 

-formic  acid,  158. 
Hydroxyl,  37. 
Hydroxylamine,  103. 
Hydroxy-methyl-tetra- 
hydro-quinoline, 
406. 


426 


INDEX 


a-Hydroxy-propionic 

acid,  163. 
/3-Hydroxy-propionic 

acid,  164. 
Hydroxy-propionic 

acids,  162. 
Hydroxy-quinolines, 

405. 

-succinic  acids,  173. 
-sulphonic  acids,  167. 
-tribasic  acids,  181. 
Hyenic  acid,  131. 
Hyoscyamine,  418. 
Hypogseic  acid,  238. 


Idonic  acid,  196. 
Idose,  196. 

Imino  compounds,  99. 
Inactive  compounds, 
India  rubber,  355.   [127. 
Indican,  381. 
Indigo,  381. 
Indigo-blue,  382. 

-white,  383. 
Indigotin,  382. 
Indol,  384,  385. 
Indoxyl,  383.  [180. 

Internal   compensation, 
Inulin,  190. 
Inversion,  198. 
Invert  sugar,  198. 
Invertase,  40,  198. 
lodo-benzene.  280. 

-cyclohexane,  275. 

-ethane,  30. 

-methane,  28. 
lodoform,  28.  [280. 

lodonium  hydroxide, 
lodoso-benzene,  280. 
lodoxy-benzene,  280. 
Isatine,  328. 
Isethionic  acid,  167. 
Isobutane,  115. 
Isobutyl  alcohol,  125. 

-carbinol,  128. 
Isobutyric  acid,  134. 
Isocrotonic  acid,  239. 
Isocyanates,  93. 
Isocyanides,  90. 


Isodiazo-benzene,  294. 

Lutidines,  350,  353. 

-benzene-oxide,  294. 

Lyddite,  307. 

Isohexane,  118. 

Isoleucine,  209. 

M 

Isomerism,  31. 

Physical,  166. 

Magenta,  366. 

Isonitroso     compounds, 

Maleic  acid,  174,  241. 

102. 

anhydride,  244. 

Iso-paraffins,  119. 

d-Malic  acid,  176. 

Isopentane,  117. 

i-Malic  acid,  175. 

Isophthalic  acid,  335. 

Z-Malic  acid,  174. 

Isoprene,  355. 

Malonic  acid,  143,  145. 

Isopropyl  alcohol,  121. 

Malonic  anhydride,  146. 

Isopurpurin,  413. 

Malonyl  urea,  223. 

Isoquinoline,  401,  406. 

Malt,  200. 

Isosuccinic  acid,  147. 

Maltase,  200. 

Isosulphocyanates,  94. 

Maltose,  200. 

Itaconic  acid,  244. 

Mandelic  acid,  332. 

anhydride,  183,  245. 

Ma^na,  155. 

Mannite,  155. 

hex-acetate,  156. 

hexa-nitrate,  155. 

Kairine  406. 

Mannitol,  155. 

Kerosene   111. 

Mannoheptite,  156. 

Ketone  alcohols,  186. 
Ketones,  71,  346. 
Ketoses,  186. 

Mannonic  acids,  171. 
Manno-saccharic     acid, 
Mannoses,  195.        [155. 
Margaric  acid,  131. 

Marsh  gas,  21,  24. 

L 

series,  109. 

Lacmoid,  312. 
Lactam  compounds,  329. 
Lactic  acid,  163. 
acids,  162. 

Martius'  yellow,  399. 
Melamine,  216. 
Melissic  acid,  131. 
Mellite,  337. 
Mellitic  acid,  337. 

/-Lactic  acid,  164. 
Lactim  compounds,  329. 

Melting-points,  9. 
Menthadiene,  355. 

Lactones,  168. 

Menthane,  355. 

Lactose,  199. 

Menthene,  355. 

Lard,  153. 

Menthol,  359. 

Laurie  acid,  130. 

Mercaptans,  75. 

Lead  plaster,  149. 

Mercury  ethyl,  106. 

sugar  of,  60. 

fulminate,  103. 

Lepidine,  401,  405. 

Mesaconic  acid,  244. 

Leucine,  209. 

Mesitylene,  255,  270. 

Levo  compounds,  135. 

Mesitylenic  acid,  270, 

Levulpse,  190. 

333. 

Light  oil,  251. 

Mesotartaric  acid,  180. 

Limonenes,  356. 

Mesoxalic  acid,  176. 

Linolei'c  acid,  251. 

Meta-amino-benzoic 

Litmus,  313. 

acid,  329. 

INDEX 


427 


Meta-di-hydroxy-ben- 
zene,  311. 

-hydroxy-benzoic 

acid,  342. 
Metaldehyde,  50. 
Metamerism,  32. 
Meta-phthalic  acid,  335. 

-series,  267. 

-styrene,  375. 
Methanal,  47. 
Methane,     21,     24,     29, 

109. 

Methanic  acid,  55. 
Methanol,  35. 
Methoxy-benzoic     acid, 
305,  343. 

-tetra-hydro-quino- 

line,  406. 
Methyl  acetate,  69. 

-acetylene,  249. 

alcohol,  3,  35,  129. 

alcohol  series,  129. 

-amine,  90,  96. 

-ammonium  salts,  97. 

-arbutin,  416. 

-benzene,  264. 

bromide,  28. 

-carbinol,  128. 

chloride,  25,  28. 

cyanide,  88. 

-diethyl-methane, 
118. 

-divinyl,  356. 
Methylene  iodide,  28. 
Methyl  ether,  46. 

-ethylene,  233. 

ethyl  ether,  46. 

-ethyl-pyridine,  350. 

-glycocoll,  208. 

green,  369. 

-indol,  385. 

iodide,  28. 

-isopropyl-benzene, 
274. 

-naphthalenes,  401. 

-pentamethylene, 
275. 

-phenyl  ether,  305. 

-phenylhydrazine, 
298. 

-phosphine,  104. 


-propanic  acid,  134. 

-pyrocatechol,  311. 

-quinolines,  401,  404. 

sulphide,  76. 

-sulphuric  acid,  69. 

-toluenes,  266. 

violet,  369. 
Milk  sugar,  199. 
Mirbane,     Essence     of, 

285. 

Mixed  ethers,  46. 
Mixing  syrup,  188. 
Molasses,  198. 
Molecular    weights,  de- 
termination of,  13. 
Monosaccharides,  185. 
Mordants,  367. 
Morphine,  418. 
Moth  balls,  391. 
"  Mother-of-vinega» ," 

58. 

Mucic  acid,  184. 
Musk,  artificial,  286. 
Mustard-oils,  94. 
Mutton  tallow,  153. 
Mycoderma  aceti,  58. 
Myricyl     alcohol,     128, 

129. 

Myristic  acid,  131. 
Myronic  acid,  416. 
Myrosin,  416. 

N 

Naphtha,  111. 
Naphthalene,  388. 
Naphthazarin,  401. 
Naphthenes,  275. 
Naphthionic  acid,  398. 
Naphthols,  398. 

oranges,  399. 

-sulphonic  acid,  399. 

yellow  S,  400. 
Naphthoquinones,  400. 
Naphthylamines,  397. 

-sulphonic  acid,  398. 
Narcotine,  406,  419. 
Nee-paraffins,  119. 
Nicotine,  418. 
Nicotinic  acid,  351. 
Nitriles,  89. 


Nitro-benzene,  285. 

-benzoic  acids,  326. 

-benzyl  alcohol,  317. 

-cellulose,  201. 

-chloroform,  102. 

-cinnamic  acids,  378. 

compounds,  99,  101. 

-cuminic    aldehyde, 

309. 

Nitroform,  102. 
Nitrogen,  estimation  of. 

11. 
Nitro -glycerin,  150, 152. 

-mannite,  155. 

-methane,  102. 

-naphthalene,  394. 

-phenols,  306. 

-pheny  1-pro  pio  lie 

acid,  381. 
Nitroso      compounds, 

102. 
Nitro-tolueiies,  286. 

-trichlormethane,  102, 
Nonane,  109. 
Nonoic  acid,  130. 
Nonose,  186. 
Nonyl  alcohol,  129. 
Normal  paraffins,  119. 
Nux  vomica,  419. 

O 

Octane,  109. 
Octoic  acid,  130. 
Octonaphthene,  275. 
Octose,  186. 
Octyl  alcohol,  129. 
CEnanthylic  acid,  130. 
Oils,  Drying,  251. 
Olefiant  gas,  230,  231. 
Olefines,  230. 
Olefin-terpenes,  357. 
Oleic  acid,  148,  240. 
Ole'in,  153,  238,  240. 
Oleomargarin,  153. 
Opium  alkaloids,  418. 
Optical  activity,  127. 
Orange  III,  301. 
Orcein,  313. 

Orcinol,  313.    [acid,  327. 
Ortho-amino-benzoic 


428 


INDEX 


Ortho-benzoquinone, 

Para-toluidine,  289. 

349. 

Paris  green,  60. 

-di-hydroxy-benzene, 

Partial  distillation,  6. 

310. 

Pelargonic  acid,  130. 

-hydroxy-benzoic 

Pent-acetyl-glucose, 

acid,  338. 

189. 

-phthalic  acid,  334, 

Penta-methylene-di- 

-series,  267. 

amine,  350. 

Osazones,  194. 

Pentane,  21,  109,  117. 

Osones,  195. 

Pentanes,  116. 

Oxalates,  145. 

Pentene,  230. 

Oxalic  acid,  143. 

Pentoses,  186,  187. 

Oxal-ureid,  223. 

Pentyl  alcohol,  129. 

Oxaluric  acid,  223. 

alcohols,  126. 

Oxalyl-urea,  223. 

Peptones,  420. 

Oxamic  acid,  215. 

Peruvian      bark      alka- 

Oxanthranol, 410. 

loids,  417. 

Oximes,  103. 

Petroleum,  3,  110. 

Oxindol,  332,  384. 

Phenacetin,  308. 

Oxy-acetic  acid,  160. 

Phenanthraquinone, 

-acids,  157. 

413. 

-benzoic  acid,  342. 

Phenanthrene,  413. 

-haemoglobin,  419. 

Phenetidine,  308. 

-propionic  acids,  162. 

Phenetol,  292. 

Phenol,  302. 

P 

Phenolates,  305. 

Phenol-acids,  337. 

Palmitic  acid,  131,  135. 

-phthalem,  369. 

Palmitin,  149,  153. 

Phenols,  302. 

Papaverine,  406. 

Mon-acid,  302. 

Paper,  202. 

Di-acid,  310. 

Para-amino-benzoic 

Tri-acid,  313. 

acids,  329. 

Phenol-sulphonic  acids, 

Parabanic  acid,  223. 

308. 

Para-cyanogen,  80. 

Phenyl  acetate,  306. 

-di-hydroxy-benzene, 

-acetic  acid,  332. 

312. 

-acrylic  acid,  376. 

Paraffin,  111. 

-acetylene,  380. 

Paraffins,  109. 

-butylene,  375. 

Paraformaldehyde,  47. 

-carbinol,  316. 

Para-hydroxy-benzoic 

Phenylene,  408. 

acid,  343. 

Phenyl-ethyl       alcohol, 

Paraldehyde,  50. 

317. 

Para-leucaniline,  364. 

-ethylene,  374. 

-methyl-isopropyl- 

Phenylfructosazone, 

benzene,  274. 

194. 

-nitro-toluene,  284. 

Phenylglucosazone,  194. 

-oxy  benzoic  acid,  343. 

Phenyl-glycolic    acid, 

-phthalic  acid,  336. 

332. 

-rosaniline,  365. 

Phenylhydrazine,  297. 

-series,  267. 

Phenylhydrazones,  193. 

Phenyl     hydrosulphide, 
308. 

-hydroxyl-amine,  297. 
Phenyl-iodoso    chloride, 
280. 

-ketones,  346. 

-mercaptan,  308. 

-methane,  264,  362. 

-methyl  ketone,  346. 

-propiolic  acid,  380. 

-propionic  acid,  333. 

-propyl  alcohol,  317. 

-propylene,  375. 

-salicylate,  341. 

-tolyl  ketone,  346. 

-vinylacetic  acid,  390. 
Phloretic  acid,  416. 
Phloretin,  314,  416. 
Phloridzin,  314,  416. 
Phloroglucinol,  314. 
Phosphines,  104. 
Phosphorus  compounds, 

104. 

Phthale'ins,  335,  369. 
Phthalic  acid,  334. 

acids,  226,  334. 

anhydride,  335. 
Physiological  chemistry, 

419. 

Picolines,  350,  352. 
Picrates,  307. 
Picric  acid,  307. 
Pimelic  acid,  143. 
Pineapple  essence,  134. 
Pinene      hydrochloride, 

357,  358. 
Pinenes,  356. 
Piperic  acid,  407. 
Piperidine,  353,  419. 
Pipeline,  419. 
Piperonal,  344. 
Polymerism,  32. 
Polypeptides,  226. 
Polysaccharides,    185, 

196,  200. 

Polyterpenes,  355. 
Potassium  cyanide,  82. 

ferricyanide,  83. 

ferrocyanide,  84. 
Primary  alcohols,  123. 

ammonia  bases,  100. 


INDEX 


429 


Propandiolic  acid,  170. 
Propane,  21,  109. 
Propanic  acid,  131. 
Propanol,  121. 
Propanone,  71. 
Propantriol,  148. 
Propargyl  alcohol,  250. 
Propene,  230. 
Propiolic  acid,  250. 
Propionic  acid,  130,  131. 
Propyl  alcohol,  73,  121, 
129. 

-meta-cresol,  309. 

-piperidine,  353. 

-pyridine,  353. 
Propylene,  230,  233. 
Protocatechuic     acid, 

343. 

Prussian  blue,  84. 
Prussiates  of  potash,  83. 
Prussic  acid,  81. 
Pseudocumene,  255, 273. 
Purification      of      com- 
pounds, 4. 
Purine,  225. 
Purpurin,  413. 
Pyrene,  29. 
Pyridine,  350,  351. 

bases,  350. 

-dicarbonic  acid,  403. 
Pyrocatechol,  310. 
Pyrogallic  acid,  313. 
Pyrogallol,  313. 
Pyroligneous  acid,  3. 
Pyrotartaric    acid,  143, 

148. 
Pyroxylin,  201. 

Soluble,  201. 

Q 

"Quick- vinegar  pro- 
cess," 58. 

Quinaldine,  401,  404. 

Quinine,  417. 

Quinizarin,  412. 

Quinoline,  334,  401. 

Quinolinic  acid,  351, 
403. 

Quinone,  348. 

Quinones,  347. 


R 

Racemic  acid,  178. 
Radicals,  38,  141,  152. 
Red    prussiate    of  pot- 
ash, 83. 
Residues,  38. 
Resorcinol,  311. 
Resorcinol-phthalei'n, 
Rhamnite,  154.        [372. 
Rhamnose,  187. 
Rhigoline,  111. 
Rhodamine  dyes,  308. 
Rhodinol,  308. 
Ribose,  187. 
Roccellic  acid,  143. 
Rochelle  salt,   178. 
Rosaniline,  290, 365, 366. 
Rosin,  357. 
Ruberythric  acid,  410. 

S 

Saccharic  acid,  184. 
Saccharin,  331. 
Saccharobioses,  197. 
Saccharose,  197. 

oct-acetate,  199. 
Saccharotrioses,  197. 
Salicin,  415,  416. 
Salicylic  acid,  338. 

aldehyde,  339. 
Salol,  341. 
Saponification,  70. 
Saponin,  417. 
Sarco-lactic  acid,  163. 
Sarcosine,  208. 
Saturated     compounds, 

228. 

Schweinfurth's  green,60. 
Sebacic  acid,  143. 
Secondary  alcohols,  122. 

ammonia  bases,  100. 

butyl  alcohol,  125. 

propyl  alcohol,  73, 121 . 
Seidlitz  powders,  178. 
Seignette  salt,  178. 
Serine,  209. 
Sesquiterpenes,  355. 
Silicon  tetrethyl,  106. 
Skatol,  385. 


Smokeless  powder,   153, 

201. 

Soaps,  136. 

Sodium  chloride  glucose, 
189. 

ethyl,  105. 

glucose,  189. 

glycol,  138. 

methyl,  59. 
Soluble  blue,  84,  369. 

cotton,  201. 

starch,  204. 
Sorbic  acid,  251. 
Sorbite,  156. 
Sources  of  compounds, 

3. 

Specific  gravities  and 
molecular  weights, 
13. 

Sperm  oil,  153. 
Spirit  of  wine,  39. 
Starch,  202. 
Stearic  acid,  131,  135. 
Stearin,  149,  153. 

candles,  135. 
Stereo-chemistry,  167. 
Structural  formulas,  15. 
Structure  of  compounds, 

16. 

Strychnine,  419. 
Stupp,  413. 
Styphnic  acid,  312. 
Styrene,  374. 
Styryl  alcohol,  375. 
Suberic  acid,  143. 
Substantive  dyes,  368. 
Substituted    ammonias, 

96. 

Substitution,  27. 
Succinamide,  216. 
Succinate,  Basic  ferric, 

147. 
Succinic  acid,  143,  146. 

acids,  146. 

anhydride,  147. 
Succinimide,  216. 
Sucrates,  199. 
Sugar  of  lead,  60.    ' 

of  milk,  199. 
Sugars,  185. 
Sulphanilic  acid,  301. 


430 


INDEX 


Sulpho-benzoic    acids, 
326,  331. 

-cyanates,  87,  93. 

-cyanic  acid,  86. 
Sulphones,  76. 
Sulphonic  acids,  77,  298. 
Sulpho-urea,  87,  224. 
Sulphur  alcohols,  75. 

ethers,  76. 
Sulphuric  ether,  43. 
Synthesis,  26. 


Tallows,  153. 
Talose,  196. 
Tannic  acid,  346. 
Tannin,  346. 
"Tartar,"  177. 

Cream  of,  178. 

emetic,  178. 
d-Tartaric  acid,  177. 
i-Tartaric  acid,  180. 
Z-Tartaric  acid,  180. 
Tartrates,  178. 
Tartronic  acid,  152,  173. 
Taurine,  168,  210. 
Taurocholic  acid,  210. 
Tautomerism,  92. 
Teracrylic  acid,  238. 
Terecamphene,  359. 
Terephthalic  acid,  336. 
Terpanes,  357. 
Terpenes,  355. 
Tertiary  alcohols,  126. 

ammonia  bases,  100. 

butyl  alcohol,  125. 
Tetra-brom-fluorescei'n, 
373. 

-chlor-methane, 
29. 

-ethyl-ammonium  hy- 
droxide, 98. 

-ethyl-ammonium 
iodide,  98. 

-ethyl-phosphonium 

hydroxide,  104. 
Tetrahydro-benzenes, 
275. 

isoquinoline,  406. 

-quinolino,  405. 

-toluene,  275. 


Tetra-hydroxy-dibasic 

acids,  183. 

Tetra-methyl-ethane, 
118. 

-methyl-methane, 
117. 

-nitro-methane,  102. 

-phenyl-methane, 

362. 

Tetrolic  acid,  250. 
Tetroses,  186. 
Thalline,  406. 
Theine,  226. 
Theobromine,  226. 
Thiophene,  256. 
Thiophenol,  308. 
Thio-urea,  224. 
Thymol,  309. 
Tin  tetrethyl,  106. 
Toluene,  255,  264. 

-sulphon-amide,  300. 

-sulphon-chloride,299. 

-sulphonic  acid,  299. 
a-Toluic  acid,  332. 
Toluic  acids,   266,   300, 

331. 

Toluidines,  289. 
Tolyl-carbinol,  318. 

-cyanide,  300. 
Tri-acetamide,  213. 

-amino-triphenyl-car- 
binol,  366. 

-amino-triphenyl-me- 
thane,  364. 

-brom-phenol,  306. 

-carballylic  acid,  154. 

-chloracetic  acid,  63. 

-chloraldehyde,  54. 
Trichlorhydrin,  150. 
Tri-chlor-methane,  28. 

-chlor-propane,  150. 

-cyanhydrin,  154. 

-cyan-triamide,  216. 

-ethyl-amine,  96. 
Trihydroxy-anthraquin- 
one,  413. 

-benzene,  313. 

-benzoic  acids,  345. 

-purin,  225. 
Tri-keto-hexamethyl- 
ene,  315. 


Trimesitic  acid,  270. 
Trimethyl-amine,  98. 

-benzene,  270. 

-carbinol,  128. 

-ethyl-methane,  118. 

-phosphine,  104. 

-xanthine,  226. 
Trinitro-methane,  102. 

-phenol,  307. 

-resorcinol,  312. 

-triphenyl-methane, 

364. 

Trioses,  186. 
Triphenyl-carbinol,  364. 

-carbinol-carbonic 
acid,  370. 

-methane,  362,  363. 

-methane  dyes,  365. 
Trivalent  radicals,  152. 
Tropseolin  D.,  301. 
TropaBolin  OO,  302. 
Tropic  acid,  418. 
Tropine,  418. 
Turnbull's  blue,  84. 
Turpentine,  357. 

U 

Univalent  radicals,  141. 
Unsaturated         com- 
pounds, 228. 
Uranin,  372. 
Urea,  86,  218. 

salts,  221. 

Substituted,  221. 
Ureids,  222. 
Urethanes,  206. 
Uric  acid,  224. 
Uvitic  acid,  270. 


Valeric  acid,  130,  134. 
Valylene,  251. 
Vanillic  acid,  344. 
Vanillin,  344. 
Veratric  acid,  311. 
Veratrol,  311. 
Verdigris,  60. 
Veronal,  223. 
Vinasse,  98,  198. 
Vinegar,  59. 


INDEX 


431 


Wine,  spirit  of,  39. 

vinegar,  58. 
Wintergreen  oil,  338. 
Wood  gum,  204. 

spirits,  3,  35. 


Xanthine,  225. 
Xanthogenic  acid,  158. 
Xanthone,  340. 
Xylenes,  255,  265. 
Xylidines,  290. 
Xylite,  154. 
Xylose,  187. 


Yellow  prussiate  of  pot- 
ash, 83. 


Zinc  ethyl,  105. 


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